International Research Journal of Plant Science (ISSN: 2141-5447) Vol. 4(6) pp. 168-191, June, 2013
Available online http://www.interesjournals.org/IRJPS
Copyright © 2013 International Research Journals
1*
2
1
Department of Biology, King Abdulaziz University, Jeddah, Saudi Arabia.
2
Centre for Plant Diversity and Systematics, University of Reading.
*Corresponding Author Email: aaldhebiani@kau.edu.sa
Abstract
The genus Euphorbia is the largest in Saudi Arabia, even though no anatomical study has been done intensively. In this study the epidermis, the stomata and the venation patterns have been investigated.
The shape of the epidermal cell in Euphorbia species in Saudi Arabia varies: polygonal, rectangular, undulate or elongated. Moreover, the cell shape relies on the cell location on a leaf, i.e. the middle
INTRODUCTION
Euphorbiaceae, the spurge family, one of the major flowering plant families: with 334 genera grouped in 52 tribes and 5 subfamilies, is considered as the sixth largest family of Angiospermae. In Saudi Arabia,
Euphorbiaceae is represented by 15 genera (
L., region, the margin, the apex or above the vein. Furthermore, in some cases both leaf surfaces have the same cell shape but more often they are unlike. Hairs are generally simple, unbranched and with a warty ornamentation on their surface. Papillae occur only in one species E. hypericifolia .The most common stomata type is anomocytic, while the rare type is actinocytic, recorded only in E. helioscopia .
Stomata of more than one type (have been encountered on the same leaf surface as in E. scordiifolia and E. hirta . Venation patterns vary from one-veined, three-veined to those with four or more veins.
Keywords: Euphorbia, Saudi Arabia, stomata, venation, epidermal cells, anatomical characters.
Flueggea Willd,
Neck. ex Juss.,
L., Micrococca
Phyllanthus
Ricinus L.,
Benth.,
L., Clutia
Mercurialis
Acalypha
L.,
L.,
L.,
Andrachne
Chrozophora
Erythrococca
Tragia L.,
Dalechampia L., Jatropha L., Croton L. and Euphorbia L.)
(Chaudhary, 2001). Among them, Euphorbia is the largest and varies from herbs to shrubs and trees, and from succulent to non-succulent plants. Species are scattered all over the country but the succulent taxa mostly occur in the South West Region. According to
Govaerts et al., (2000), the genus Euphorbia L. is the third largest genus in the flowering plants (after
Astragalus [Fabaceae] and Psychotria [Rubiaceae]) with species can be prostrate or erect, monoecious or dioecious and succulent or non-succulent. Most of the succulent Euphorbia
Even though the genus Euphorbia is the largest in
Saudi Arabia, no extensive study on the anatomy of the genus has been done.
This work has been done to revise the genus
Euphorbia in Saudi Arabia in three parts: morophological, anatomical paper. and species are endemic to Africa. phytochemical studies. The phytochemistry study has been published in a separate
In the Euphorbiaceae, anatomical characters have been found significant since the work of Pax, (1884). In his work, Pax found the importance of laticifers as a character to define natural groups. In addition, he used about 2000 species distributed worldwide, both in Old and New Worlds, and mainly in the tropical, subtropical and warm temperate regions. In addition to the wide distributional range, Euphorbia L. has various life forms, as annual or perennial herbs, shrubs or trees. The the type of laticifers (articulate or non-articulate), phloem characters and trichome type as the major anatomical features to support his redivison of the major suprageneric taxa in the family. The first significant anatomical survey of the family was provided by
Solereder, (1899) who revised the groups of Radlkofer,
(1870) and added many observations by himself. Then,

Gaucher, (1902) tried to omit all the work of the German school by publishing an independent anatomical survey of the family. His work was criticized by Solereder,
(1908). Yet, it was valuable in providing a comparative review of anatomical characters which was arranged by tribe. Later, in a series of studies, Mahlberg, (1973; 1974;
1975; 1982) and Mahlberg et al., (1987) showed the systematic importance of laticifers in Euphorbia , especially with regard to the starch grains produced.
Furthermore, the vascular anatomy of petioles has been studied in cross section by Dehay, (1935) who found a considerable variation in stellar configurations. However, it seems unlikely that this feature will be of general value.
Meanwhile, Miller and Webster, (1962) have used differences in petiolar steles to separate Cridoscolus from
Jatropha . Then, Dehgan, (1982) could prove that the petiolar stellar dissection were significant at the sectional and sub-sectional level in some genera, such as
Jatropha . However, in a considerable number of taxa, stipules have become reduced or are early deciduous.
For example, many species lack stipules, whereas they are large and remarkable in others. In Euphorbia , the presence or absence of stipules is a diagnostic character for some sections and subgenera (Webster, 1994a).
Anatomical Characters in Euphorbia
Latex
The white latex is a useful distinguishing character in the genus Euphorbia L. It is distributed throughout the plant in a series of tubes derived from either single cells (nonarticulated laticifers) or articulated laticifers formed by the fusion of several cells. The value of laticifer types as a taxonomic marker in systematic comparisons between and within families has been established by Carlquist,
(1961).The laticifer system of the mature Euphorbia plant was explained by Gaucher, (1898; 1902). In addition,
Rosowski, (1968) studied the branched non-articulated laticifers system in mature tissue of the internode and node in transition from the node to and throughout the mature leaf of E.supina
Raf. He found that the latex system in the E. supina stem is restricted to the cortex and does not break through the leaf gaps. In the leaf lamina he found that the widest laticifers are in association with the vascular system. These laticifers begin to branch from the base of the leaf and continue throughout certain areas in the mesophyll. Moreover, they are associated with the phloem and may send some branches at right angles to the vein and between the bundle-sheath cells.
Epidermis
Epidermal cells may vary greatly in size, shape and
Aldhebiani and Jury 169 outline from species to species, especially when seen in a surface view. Generally, in dicotyledons, epidermal cells have irregular shapes and sizes. Sometimes the shape of the cells in both leaf surfaces are similar, but more often they are different. The costal cells usually differ from those intercostal regions; they tend to be elongated in the direction of the veins. Some marginal cells develop unicellular or multicellular prickles. Moreover, anticlinal walls can be either very thin and hardly visible from the surface or they may range through degrees of thickness to be very thick (Kakkar and Paliwal, 1972).
One of the important epidermal features for all taxonomists is the hairs. They can be glandular or nonglandular; and can be divided depending on the component number of cells and degree of branching. The occurrence of distinctive types of hair can be a valuable character to recognize a whole family. Moreover, hairs are more useful in determination at the level of genus or species. In other words, variations in size and density should be accepted in the differentiation of closely related genera or species after a comprehensive investigation of a wide range of material (Metcalfe and Chalk, 1950).
In a study of 150 species of Euphorbia, Kakkar and
Paliwal (1974) described the epidermal cells in Euphorbia as circular, trapezoidal, rectangular or polygonal in outline. Additionally, they found that the shape may vary depending upon the location of the epidermal cell on the leaf, i.e. the middle region, margin, apex or above the vein. Some xeromorphic species exhibit a waxy covering which takes on many crystalline forms. Hairs were also recorded in the epidermis of Euphorbia in some species.
In addition, the papillae occurred in the surface view as rounded structures in the centre of cell lumen.
Stomata
A stoma consists of the stomatal aperture and the pair of guard cells that form it. Stomata usually tend to be on the lower surface only. But in some cases this distribution varies from species to species and depends on whether the plant is a xerophyte or a mesophyte. They might be superficial or sunken. Stomata sometimes are surrounded by specialized epidermal cells which are called subsidiary cells. These subsidiaries differ from unmodified epidermal cells in shape, size and staining properties (Baranova, 1992; Metcalfe and& Chalk, 1950;
Stace, 1965). On the other hand, the arrangement of subsidiary cells, where present, is of the greatest interest to the taxonomist. This variation is used to define the different types of stomata. Occasionally species have several types of stomata on one leaf, while some have only one type for the species (Stace, 1984). In addition,
Van Cotthem, (1973) pointed out that those morphological stomata types can provide not only diagnostic characters but also very valuable taxonomic ones or even phylogenetic clues. Metcalfe and Chalk,

170 Int. Res. J. Plant Sci.
(1950) had established some terms to replace the representative ‘family’ name proposed by Vesque,
(1889). Anomocytic was substituted for the ranunculaceous type; anisocytic replaced cruciferous, diacytic the caryophyllaceous and finally paracytic for the rubiaceous. The tetracytic type which can be found in most of the monocotyledons was added by Metcalfe,
(1960). Later, Stace, (1965) proposed the term cyclocytic for the narrow ring of four or more subsidiary cells surrounding the stomata. Metcalfe and Chalk, (1950) have named and defined the actinocytic type as stomata surrounded by a circle of radiating cells. Three more types were introduced by Van Cotthem, (1970), hexacytic, epicytic and hemiparacytic. And some intermediate types were added by Payne, (1970) who described the helicocytic and allelocytic types in relation to mesogenous forms of anisocytic, paracytic and diacytic patterns. Stace, (1989) lists 35 types of stomata in vascular plants. Closely related families are distinguished by the presence of a specific type of stomata; such as
Acanthaceae and Scrophulariaceae separated by the presence of diacytic stomata in the former as against anomocytic in the latter. Moreover, some stomatal types are distinctive of certain families: for example, Ranuculaceae has the anomocytic type, Brassicaceae the anisocytic,
Caryophyllaceae diacytic, Rubiaceae paracytic and finally
Poaceae has the graminaceous type (Singh, 2004).
According to Metcalfe and Chalk (1950), the mature stomata of Euphorbiaceae, are anomocytic, paracytic and anisocytic. They are usually confined to the lower leaf surface, more rarely on both surfaces of the lamina.
Paracytic stomata were reported by Tognini, (1897) which are mesogenous in development in E. variegata and Ricinus communis . On the other hand, according to
Raju and Rao (1977), stomata in the Euphorbiaceae show considerable variation. They found that the woody taxa have predominantly the paracytic stomata type, while the anisocytic stomata are characteristic of the herbaceous Phyllanthoideae . Moreover, they indicated that Chamaesyce has a high percentage of anomocytic stomata (Raju and Rao, 1987). Finally, a considerable diversity of stomatal types were found in Euphorbia by
Kakkar and Paliwal, (1974). They reported that the common type of stomata in Euphorbia species is the anomocytic, even though stomata of paracytic and anisocytic have been also observed.
Venation
Some features that give the leaf its structure are, for instance, leaf shape, margin type and venation patterns.
These together form the leaf architecture as discussed by
Hickey, (1979). A more sophisticated knowledge of leaf architecture has allowed a start in discriminating phylogenetic trends from leaves (Hickey, 1973; Roth-
Nebelsick et al., 2001). Due to its importance, especially for systematic classification, attention has been paid largely to the architectural properties of leaf venation
(Köhler, 1993). The careful description of venation in cooperation with studies of other leaf anatomy details can provide valuable taxonomic evidence. The works of Pray
(1955a; 1955b) suggest that the venation can be useful in a comparative analysis. Moreover, Wagner (1979) has proved that the vein patterns were significant for classification at the level of species, genus and family in ferns. Of course, this is more noticed and observed in angiosperms especially dicotyledons where the hierarchical network patterns of the veins are much more advanced and complicated.
Leaf venation has been neglected for a long time in the Euphorbiaceae until the work of Levin, (1986a;
1986b; 1986c). Levin developed a new insight into relationships within subfamily Phyllanthoideae. No detailed studies have been provided for other subfamilies, except the work of Sehgal and Paliwal
(1974) on the tribe Euphorbieae. In part II of their study on the leaf anatomy of Euphorbia , Sehgal and Paliwal designated the venation in petiolate leaves as uni-, bi- and tri-veined according to the number of strands entering the petiole or lamina base. They noticed that in the 150 species under investigation, the majority bear leaves belonging to the tri-veined category. Moreover, they divided the latter into ornamented and unornamented veins. When the veins are surrounded by a parenchymatous sheath it is called ornamented. And when this sheath is absent it is unornamented. Besides, sometimes trachedial nodules are encountered at the apices and in the serrations of the leaf. Small veins usually form networks in the lamina. These networks may vary in size and shape, and subdivide the area of the mesophyll. The thinnest branches of the bundles bounded by the smallest areas or regions are called areoles. These areoles usually contain blind vein endings. The degree of branching of these vein endings varies in the leaves of different species. Therefore, this can be a useful identification tool.
MATERIAL AND METHODS
Herbarium specimens were obtained from Kew (Kew
Garden herbarium, UK) and RIY (National Herbarium in
Riyadh). Since leaves are early deciduous in succulent species, most of the herbarium sheets or spirit collections of these species have no leaves. As a result, these species were omitted from this anatomy study, except for the stick-like Euphorbias: E. balsamifera subsp. adenensis , E. schimperi, “E. aff . schimperi”, “E. aff . consobrina” and E. cuneata . Only mature leaves were used for studying the epidermis, stomata and venation.
Epidermal peel
This method was used to observe stomata, epidermal

cells and hairs.
1- Leaves were rehydrated using polyoxyethylene sorbitan monolaurate (Tween20) in water and heated for
30 minutes. Then, washed by water and conserved in
70% ethanol for future work.
2- Both surfaces of the leaf were scraped and peeled off under a dissection microscope with the aid of fine forceps and a razor blade to remove loose cells.
3- Samples were bleached by Jeffery’s Solution or the bleaching agent Vortex for 10-20 minutes depending on leaf thickness. Sometimes this was overnight.
4- Samples were washed, mounted and observed under a light microscope.
5- Photographs were taken using a Leitz Diaphlan polarizing microscope or a Reichert Polyvar 2
Microscope.
Staining by alucin blue was tried, but without success. Samples became too dense or obscure due to the presence of tannins and other compounds in the herbarium specimens. Therefore, some samples were left without staining.
Leaf clearing
The following method was adopted from Radford et al.,
(1974), with some modifications for use on herbarium materials.
1- The leaf was placed in a Petri dish and covered with 5% Sodium Hydroxide (NaOH). The dish was wrapped in cling film leaving a small gap in one area for ventilation.
2- This was microwaved for five seconds on medium power.
3- The Petri dishes were left on a hot plate at 35-37 degrees centigrade for a week or until the leaf was transparent. The NaOH was changed twice a day for each sample.
4- When the leaf had cleared sufficiently, it was washed in water and covered in 90% bleaching agent
Vortex for ten minutes to one hour depending on the reaction of the sample.
5- The leaf was washed again in water. g) h) i) j) k) c) d) e) f)
6- Samples were dehydrated in ethanol series and stained as following: a) b)
30% ethanol
50% ethanol
2 minutes.
2 minutes.
1% safranin in 50% ethanol
Wash in water three times
4 minutes.
30% ethanol 2 minutes repeated 3 times.
50% ethanol 2 minutes repeated twice.
70% ethanol 2 minutes.
90% ethanol 2 minutes.
100% ethanol 2 minutes.
Absolute ethanol: histoclear 1:1 2 minutes.
Histoclear 2 minutes.
Aldhebiani and Jury 171 l) balsam.
Mounted in 100% glycerol and sealed with Canda m) Observed under light microscope. n) Photographs were taken using a Leitz Diaphlan polarizing microscope or Reichert Polyvar 2 Microscope.
Scanning Electron Microscopy
1- Dry specimens were mounted surface up on scanning electron microscope stubs using Bostik No.1 adhesive.
2- Stubs were sputter coated for 2-3 minutes with a gold palladium alloy using an Edwards sputter coater to give a coating about 15-20 nm thick.
3- Samples were examined in FEI Quanta FEG 600
Environmental Scanning Electron Microscope (ESEM) in high vacuum SEM mode.
4- Photographs were taken using the computerized digital system of the microscope.
RESULTS
Epidermis
Results of the epidermal characters in Euphorbia species under investigation are summarized in Table 1.
Cell shape
Depending upon the shape of the cell wall and considering the results from Kakkar and Paliwal, (1974), the shape of the epidermal cell varies: polygonal, rectangular, undulate or elongated. Moreover, the cell shape relies on the cell location on a leaf, i.e. the middle region, the margin, the apex or above the vein.
Furthermore, in some cases both leaf surfaces have the same cell shape but more often they are unlike. This combination of cell shape characters gives each species its unique leaf surface appearance.
The normal straight cell walls in both adaxial and abaxial surfaces are shown in the following taxa: E. schimperi, E. cuneata, E. helioscopia, E. dracunculoides and E. balsamifera subsp. adenensis see Figure 1. In addition, “ E. aff. schimperi” and “E. aff . consobrina” have also the same straight cell wall on both surfaces.
Meanwhile, E. grossheimii , E. retusa and E. pirottae have elongated cells on both leaf surfaces (Figure 2 a and b).
On the other hand, the plicate cell walls on both adaxial and abaxial surfaces occur in E. chamaepeplus, E. hypericifolia and E. peplus (Figure 2 c and d), but the walls are more folded on the lower surface. In some species, the cell wall on the adaxial surface is straight, whilst it is plicate on the abaxial such as E. hirta, E.

172 Int. Res. J. Plant Sci.
Table 1.
Epidermal characters of Euphorbia taxa in Saudi Arabia.
Subgenus
Ermophyton
Species
E. balsamifera subsp .adenensis
E. schimperi
“E.
aff.
schimperi”
“E. aff.
consobrina”
E. cuneata
E. acalyphoides
E. pirottae
E. helioscopia
E. grossheimii
E. retusa
E. dracunculoides
E. falcate
E. peplus
E. chamaepeplus
E. schimperiana
E. Arabica
E. serpens
E. scordiifolia
E. granulate
E. inaequilatera
Straight
+
Cell shape (cell wall)
Elongated Plicate
+
Unicellular
Ad.* Ab.* Ad. Ab. Ad. Ab. Ad. Ab.
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
++
++
+
+
+
+
+ +
+
+
+
+
Hairs
Multicellular
Ad.
+
+
Ab.
+
+
+
E. hirta + + + +
E. hypericifolia + ++ +
*Ab.: abaxial
*Ad. : adaxial
+ : Present
++ : the plicate folded wall is morefully developed in the lower surface than in the upper one
+? : hardly observable by LM only
Glabrous Papillae
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+?
+

Aldhebiani and Jury 173
A
B
C
E
D
Figure 1. Normal irregular epidermal cells in both adaxial and abaxial surfaces of the leaf (LM).
(A) E. balsamifera subsp . adenensis, (B) E. schimperi, (C) E. cuneata, (D) E. falcata, (E) Abaxial in E. dracunculoides

174 Int. Res. J. Plant Sci.
A
B B B
C
D
Figure 2. Error! No text of specified style in document.
Both adaxial and abaxial surfaces have the same shape of epidermal cells (LM). Elongated in A &B; plicate in C&D. (A) E. grossheimii , (B) E. pirottae , (C) E. chamaepeplus and (D) E. peplus .
schimperiana, E. helioscopia, E. inaequilatera, E. arabica, E. granulata, E. serpens and E. scordiifolia see multicellular and may appear only on one surface or both.
Furthermore, hairs in the Euphorbia species under
Figure 3 and Figure 4. This last group of species belong to subgenus Chamaesyce except for E. helioscopia and
E. schimperiana.
Hairs
Hairs on the leaf epidermis can be both unicellular and investigation are generally simple, unbranched and with a warty ornamentation on their surface. Papillae appear in
ESEM as outgrowths, whereas in the surface view they give the impression of being rounded structures at the centre of the cell. Prominent papillae occur only in one species of Euphorbia in Saudi Arabia; this species is E. hypericifolia (Figure 5 and 6), whereas in E. arabica they were poorly distinguishable using LM.

Aldhebiani and Jury 175
A
B
C
D
Figure 3. Epidermal cells vary on leaf surfaces: adaxial surface has irregular cells while the abaxial surface has plicate (LM).
(A) E. schimperiana , (B) E. arabica , (C) E. serpens , (D) E. scordiifolia.

176 Int. Res. J. Plant Sci.
Adaxial Abaxial
A
B
C
Figure 4. Epidermal cell shape varies on the adaxial and the abaxial surfaces, straight cell walls in the former while folded plicate walls occur on the latter (LM). (A) E. granulata , (B) E. inaequilatera and (C) E. helioscopia .
Hemiparacytic stomata on both surfaces
Figure 5. E. hypericifolia (LM).
Above photo: the adaxial surface with irregular epidermal cells and very clear papillae as a circle in the middle of the cell.
Lower photo: the abaxial surface with plicate cells and papillae, a hair base is obvious in the right side of the picture.

Aldhebiani and Jury 177
Adaxial
Papillae
Abaxial
Multicellular hairs in abaxial surface.
Figure 6. E. hypericifolia (ESEM), papillae on the adaxial and abaxial surfaces, multicellular hairs are on the abaxial surface of the leaf only.
Figure7. Multicellular hairs on adaxial and abaxial surfaces of E. hirta .

178 Int. Res. J. Plant Sci.
Figure 8. Hairs, wart ornamentation on hair surfaces of (A) E. scordiifolia and (B) E. pirottae ; (C) Short hairs on abaxial surface of E. balsamifera subsp. adenensis .
In E. balsamifera subsp. adenensis , the hairs are short Wax and unicellular (Figure 8C) and they are located mostly at the leaf margins and the mid-vein area on the abaxial surface only.
Hairs on the leaf of E. pirottae are present on the abaxial surface only and are both unicellular and multicellular. Euphorbia granulata is similar to E. pirottae in having both unicellular and multicellular hairs, but here they occur on both surfaces of the leaf (Figure 8B).
On the other hand, in E. scordiifolia, E. hirta and E. hypericifolia the hairs are multicellular and on both surfaces in the first two species and on the abaxial only in the latter (Figure 7). Moreover, E. hypericifolia and E. hirta have long hairs when compared with the other species (Figure 6).
No hairs were observed and leaves were glabrous in the following species: E. serpens, E. arabica, E. peplus,
E. inaequilatera, E. falcata, E. helioscopia, E. cuneata, E. retusa, E. grossheimii, E. schimperiana, E. schimperi,
E. chamaepeplus and the new variety of E. granulata.
The cuticle layer and wax in the Euphorbia species under investigation vary from smooth to densely cover in wax scales. This may be a thick smooth layer of wax which sometimes has upright scales. In some species, only the cell surface has a smooth wax layer whereas the wall between cells has upright scales of wax as in E. schimperiana, especially around the stomata pores
(Figure 9). In contrast, the anticlinal walls of some species have a smooth layer of wax, whereas the cell surface is densely covered with upright wax flakes or with some stellate wax flakes in other species.
Stomata
Stomata were observed through LM and ESEM. In the species under investigation, stomata commonly appear on both leaf surfaces (amphistomatic leaves) except in E. cuneata where the stomata are located only on the

Aldhebiani and Jury 179
A B
C D
E
Figure 9. Wax formation in Euphorbia species in Saudi Arabia: (A+B) smooth and thick in E. peplus and E. schimperi ; (C+D) smooth on top of cell while forming upright scale flakes in between, especially around stomata as in E. schimperiana .; smooth in anticlinal walls; (E) upright scale flakes in E. balsamifera abaxial surface (hypostomatic leaves). The presence and position of subsidiary cells are variable in Euphorbia types on the abaxial and three on the adaxial). The species. Subsidiary cells were found to be of unequal size and shape whether the stoma was anisocytic, paracytic, actinocytic or tetracytic. While some species distribution and type of stomata are shown in Table 2.
In addition, in some species such as E. falcata and E. helioscopia, the stomata are deeply sunken and represented only by cuticular ledges surrounding the lack them around the stomata, others have more than one arrangement of subsidiary cells.
The most common stomata type is anomocytic, while the rare type is actinocytic, recorded only in E. helioscopia . Moreover, sometimes stomata of more than one type (up to three or four types) have been encountered on the same leaf surface as in E. scordiifolia
(three types on the abaxial surface) and E. hirta (five minute pores as seen in ESEM.
Examples of species lacking subsidiary cells around stomata are: E. peplus , E. chamaepeplus , E. granulata ,
E. dracunculoides and E. acalyphoides . Therefore, they all have anomocytic stomata.
On the other hand, E. balsamifera subsp. adenensis has the mononcytic type on both leaf surfaces and anisocytic and paracytic only on the abaxial surface. In

180 Int. Res. J. Plant Sci.
Table 2.
Stomata type in Euphorbia taxa in Saudi Arabia.
Subgenus
Ermophyton
Species
E. balsamifera subsp.
adenensis
E. schimperi
“E.
sp. aff . consobrina”
“E.
sp. aff . schimperi”
E. cuneata
E. acalyphoides
E. pirottae
E. helioscopia
E. grossheimii
E. retusa
E. dracunculoides
E. falcate
E. peplus
E. chamaepeplus
E. schimperiana
E. Arabica
E. serpens
E. scordiifolia
E. granulate
E. inaequilatera
E. hirta
E. hypericifolia
*Ab. : abaxial surface
*Ad. : adaxial surface
+ : stomata present addition, E. schimperiana has anomocytic and tetracytic on the abaxial only. In contrast, E. cuneata has three types of stomata anomocytic, paracytic and anisocytic only on the lower surface.
As well, “ E. aff. consobrina”, “E. aff. schimperi”
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
Anomocytic Hemiparacytic
Ad.* Ab.* Ad. Ab.
+ +
+
+
+
+
+
+
+
+
+
+
+
+
+
Stomata
+
+
+
+
+
+
+
+
Paracytic Anisocytic Tetracytic Actinocytic Sunken
Ad. Ab. Ad. Ab. Ad. Ab. Ad. Ab. Deeply Slightly
+ +
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+ +
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+ and E. schimperi have paracytic and anisocytic only in the abaxial on the first two and in both leaf surfaces on the latter. Therefore, “ E . aff. consobrina” and “ E . aff. schimperi” are the same taxa. Then, comparing to E. schimperi results from anatomy, we can also support that a new subspecies of E. schimperi is identified.
Euphorbia serpens and E. scordiifolia are similar in having anomocytic, paracytic and anisocytic stomata, but they differ in their

Aldhebiani and Jury 181
Table.3.
Venation type in Euphorbia taxa in Saudi Arabia.
Subgenus Species
Venation
Number of veins at the leaf base
2 3 4 or more
+
Ermophyton
1
E.balsamifera subsp .adenensis
E. schimperi
E. aff. Schimperi
E. cuneata
E. acalyphoides
E. pirottae
E. grossheimii
E. retusa
E. dracunculoides
E. falcate
E. peplus
E. chamaepeplus +
E. schimperiana
E. helioscopia
+
E. Arabica
E. serpens
+
E. scordiifolia
E. granulate
E. inaequilatera
E. hirta
E. hypericifolia
E. cyathophora Poinsettia
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
Margins
Open
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
Sheathed
Closed
+
+
+
+
+
+
+
+
+
+
+
+
+
+
Extended Tracheas
Rounded Oval Elongated
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
Star shaped
+
+

182 Int. Res. J. Plant Sci.

Aldhebiani and Jury 183
Adaxial
Abaxial
A
Anomocytic
Hemiparacytic
Paracytic
Anisocytic
Tetracytic
Actinocytic
Anomocytic
Hemiparacytic
Paracytic
Anisocytic
Tetracytic
Actinocytic
B
Anomocytic
Hemiparacytic
Paracytic
Anisocytic
Tetracytic
Actinocytic
C
Anomocytic
Hemiparacytic
Paracytic
Anisocytic
Tetracytic
Actinocytic
D
D
Figure 11. Stomata types in Euphorbia taxa in Saudi Arabia: (A) E. balsamifera subsp. adenensis , (B) E. schimperi ,
(C) E. cuneata and (D) E. grossheimii .

184 Int. Res. J. Plant Sci.
Adaxial Abaxial
AnomocyticAbax ial
Hemiparacytic
Paracytic
Anisocytic
Tetracytic
Actinocytic
A
Anomocytic
Hemiparacytic
Paracytic
Anisocytic
Tetracytic
Actinocytic
B
Anomocytic
Hemiparacytic
Paracytic
Anisocytic
Tetracytic
Actinocytic
Anomocytic
Hemiparacytic
Paracytic
Anisocytic
Tetracytic
Actinocytic
D
Figure 12. Stomata types in Euphorbia taxa: (A) E. falcata , (B) E. peplus , (C) E. chamaepeplus and (D) E. schimperiana.

Aldhebiani and Jury 185
Adaxial Abaxial
Anomocytic
Hemiparacytic
Paracytic
Anisocytic
Tetracytic
Actinocytic
A
Anomocytic
Hemiparacytic
Paracytic
Anisocytic
Tetracytic
Actinocytic
B
Anomocytic
Hemiparacytic
Paracytic
Anisocytic
Tetracytic
Actinocytic
C
Anomocytic
Hemiparacytic
Paracytic
Anisocytic
Tetracytic
Actinocytic
D
Figure 13 . Figure 13. Stomata types in Euphorbia taxa in Saudi Arabia: (A) E. arabica , (B) E. serpens , (C)
E. scordiifolia and (D) E. helioscopia distribution between the leaf surfaces (see Figure 13). deeply sunken in some species, whilst in others they are
While E. hirta has the most types, E. helioscopia , E. dracunculoides and E. acalyphoides have the least.
Regarding the position of the stomata on the surface level of the epidermis, a variable degree of sunkeness has been recorded. Using the ESEM, the stomata appear only slightly sunken with the outer rims of the subsidiary cells surrounding the aperture. The deeply and slightly sunken species are recorded in Table 2. Additionally,
Figure 10 shows the sunken stomata in different species under the ESEM.

186 Int. Res. J. Plant Sci.
Adaxial
Anomocytic
Hemiparacytic
Paracytic
Anisocytic
Tetracytic
Actinocytic
A
Anomocytic
Hemiparacytic
Paracytic
Anisocytic
Tetracytic
Actinocytic
B
Anomocytic
Hemiparacytic
Paracytic
Anisocytic
Tetracytic
Actinocytic
C
Abaxial
Figure 14. Stomata types in Euphorbia taxa in Saudi Arabia: (A) E. hirta , (B) E. hypericifolia , (C) E. pirottae and (D)
E.
sp.aff
. schimperi .
Venation
The venation patterns in the Euphorbia species under investigation vary from one-veined, three-veined to those with four or more veins. The predominant type is threeveined. However, in E. balsamifera subsp. Adenensis there are seven middle parallel veins, three middle thick and four thinner lateral ones (Figure 15 A and B).
Whereas in E. pirottae, there are three main middle parallel veins and two thinner laterals (Figure 15 C). In contrast, E. chamaepeplus , E. schimperiana and E. arabica have only one thick main midrib coming from the

Aldhebiani and Jury 187
A
B
C
Figure 15 . Figure 15: Venation patterns at base of leaves in variants with more than three veins: (A & B) E. balsamifera subsp. adenensis and (C) E. pirottae.
petiole then branched from the side into two lateral veins at the point when the leaf starts widening (Figure 16).
Each of these veins branches again into secondary veins at the leaf margin.
The rest of the species have just three veins: grossheimii serpens ,
, E. dracunculoides
E. scordiifolia
E. helioscopia , E. hirta ,
,
, E. falcata
E. granulata
E. hypericifolia
,
,
, and
E. peplus
E.
,
E.
E.
E. inaequilatera ,

188 Int. Res. J. Plant Sci.
Figure 16. Venation patterns with one main mid vein at the leaf base in (A) E. arabica and (B) E. chamaepeplus .
A B
Figure 17. Venation patterns with three-veined leaves in (A) E. falcata and (B) E. granulata.
cyathophora . All the three veins come from the petiole and start branching into secondary veins both toward the falcata, E. peplus, E. chamaepeplus, E. schimperiana, E. helioscopia, E. pirottae, “E. cyathophora. aff . schimperi”, and E. margin and the mid vein direction (Figure 17 B).
The vein endings at the leaf margin vary from closed to open. There is a relationship between the closed margins and the sheathed veins (midrib and secondary CONCLUSIONS veins that are surrounded by parenchyma tissue). When the veins are ornamented (sheathed), the margins are closed. This can be seen in subgenus Chamaesyce, in species such as: E. serpens, E. scordiifolia, E. granulata,
E. inaequilatera, E. hirta, E. hypericifolia and E. arabica .
Additionally, these species have the three-vein venation.
On the other hand, when the veins are not sheathed, the veins ends are open at the leaf margin, as in: E. balsamifera subsp . adenensis, E. schimperi, E. cuneata,
E. acalyphoides, E. grossheimii, E. dracunculoides, E.
Anatomical characters are seen here to be very useful in
Euphorbia classification and identification. The results obtained from anatomical studies were useful to group some species and identify others.
Depending on the venation type, the Euphorbia species under investigation are divided anatomically into three main groups, see Figure 18.
Group one: veins are sheathed, epidermal cells differentiated on adaxial and abaxial surfaces. Group two:

Aldhebiani and Jury 189
Figure 18 . Hierarchial relation of Euphorbia taxa in Saudi Arabia based on anatomical characters.

190 Int. Res. J. Plant Sci. veins are not sheathed and epidermal cells are alike in both surfaces. And the third group includes species that do not belong to any of the previous groups. The first group can be further divided into three-veined and oneveined, while the second group into three-veined and four or more veins.
In addition, E. grossheimii , E. retusa and E. pirottae are related by being three-veined, open at the margins, with rounded to oval tracheas and elongated cells both on adaxial and abaxial surfaces. However, in E. retusa the epidermal cells have straight cell walls on the adaxial surface. They are also similar in having hemiparacytic and paracytic types of stomata either on the adaxial or the abaxial surface.
On the other hand, species with two different epidermal cells on the leaf surfaces usually have threesheathed veins with closed margins and elongated trachea, such as: E. serpens , E. scordiifolia , E. granulata ,
E. inaequilatera , E. hirta and E. hypericifolia which belong to subgenus Chamaesyce according to (Carter and
Smith, 1988).
In the case of E. granulata, which has been described as having three different variants: E. granulata var. granulata (both leaf surfaces hairy), E. granulata var. glabrata (adaxial glabrous and abaxial hairy) and a glabrous variant (the whole plant glabrous). Anatomical work has shown, especially by using the ESEM, that the leaves are either hairy or glabrous on both surfaces. So, when the leaf is hairy, both surfaces have differences in hair distribution. Usually, the lower surface is more hairy than upper surface ( E. granulata var. glabrata ), but sometimes they are evenly distributed ( E.granulata var. granulata ). In addition, hairs on both surfaces are multicellular. In contrast, when the leaf is glabrous, both leaf surfaces are glabrous and the whole plant is glabrous (suggested new variety). They were similar in having the same venation type (three-veined).
Finally, “ E . aff. schimperi “has some similarity with E . schimperi in having the same open margin not the ornamented venation type. As well, they both have the same type of stomata paracytic and anisocytic but they differ in their distribution on abaxial and adaxial. Thus, this may support the suggestion considering “ E . aff. schimperi ” as a new subspecies of E . schimperi .
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