I924]
CURRENT LITERATURE
347
between the two, and that since a plant is much less complex in its organization
than an animal, neoplasias in plant tissues offer favorable material for studies
of cell proliferation. It is claimed that crown gall in plants is commonly
analogous to benign tumors in animals, and that malignant crown gall, while
analogous to cancer, is relatively rare and is not due directly to infection by
Bacterium tumefaciens, but rather represents the result of the action of an
unknown secondary stimulus, which has altered the limited growth, begun for
purposes of protection against bacterial invasion, into a condition of limitless
proliferation.
It has long been noted that in club root caused by Plasmodiphorabrassicae
the large cells containing the parasite are always surrounded by layers of
uninfected small cells. A similar condition occurs in potato wart lesions.
The theory is advanced that these smaller cells are immune to the parasite and
tend to form a protective barrier against its further encroachments.
The treatment of animal tumors by the insertion of capillary glass tubes
filled with radium emanation demands a more complete knowledge of the
mechanism of the radium action. For this investigation, also, plant tissues
suggested themselves as favorable material. The effect of the radium emanation on both normal and diseased tissue was studied. The radium tubes were
inserted as in animal tissues, and in every case empty glass tubes of similar
size and shape were inserted into corresponding tissues as checks. Where
normal tissue was used the radium emanation invariably induced necrosis,
usually slight, but varying in degree according to the amount of radium emanation in the tube, the length of the exposure and the kind and age of the tissue.
No necrosis was observed in the checks. Inoculation of Pelargonium stems
with the crown gall organism, followed immediately by the insertion of the
radium tubes, resulted in the formation of a black necrotic area around the
tubes, but no galls were produced. Inoculated stems into which the empty
tubes were inserted developed typical crown galls. If the introduction of
the radium tube was delayed until the gall had developed, there was death of
cells and necrosis in the region immediately adjacent to the tube, but cells
beyond were morphologically unaffected. Earlier work is cited, however,
suggesting that such cells have been so influenced by the gamma rays as to have
had their proliferating power inhibited. Similar results were secured on club
roots artificially produced in cabbage and kohlrabi by inoculation with Plasmodiophora brassicae.-G. W. MARTIN.
Shape of parenchyma cells.-If college students in botany were asked to
describe the 3-dimensional shape of a typical plant cell, their replies would
probably include the range of opinion that it is "six-sided" (cubical?) to
irregularly polyhedral; a few might state that its shape is that which a plastic
sphere would assume if surroundedby other similar spheres all of which touched;
some might describe this "flattened sphere" as a rhombic dodecahedron.
The latter is indeed the opinion that dates back to KIESER and BUFFON, who
348
BOTANICAL GAZETTE
[MAY
arrived at this conception by the analogy of a stack of cannon balls, or of dry
peas which are made to swell in a closed chamber. LEWIS,4 by means of
models reconstructed from serial sections of elder pith, has studied the form of
the typical cells of one mature plant tissue. KELVIN had demonstrated
mathematically in i887 that of all bodies which may be combined to fill space
without interstices a tetrakaidecahedron, or figure having I4 surfaces, certain
of which are slightly curved, rivaled the rhombic dodecahedron of KIESERin
enclosing "the greatest space with the least extent of surface." By actual
count of the numbers of contacts which each cell of elder pith has with those
surroundingit, LEWIS has determined that these cells actually are approximately
14-sided, a mean number of I3.96 contacts having resulted from counts on
ioo cells. More than half are 13, I4, or I 5-hedra. "Cells with an excessive
number of contacts are usually large, and of such form as to suggest that an
expected division in some particular plane has failed to occur." The manner
of restitution of the tetrakaidecahedron following cell division, which produces
an II-sided figure, whether the bisecting plane be vertical or transverse, was
determined by a study of actual cell models.-F. WEISS.
Light and growth of plants.-Ever since the work of GARNER and ALLARD,
showing a close relationship between the length of day and growth and reproduction in plants, plant physiologists have felt the need of a thorough study of the
chemical conditions existing in plants exposed to light for different periods
of time. A recent paper by NIGHTINGALE5 does much to supply this need.
Using mainly the tomato, but including several other plants, he exposed the
plants to light for different lengths of time, and also varied the amount of
nitrogen in the nutrient solution. He finds that in the tomato it is the carbohydrate-insoluble nitrogen ratio, rather than the carbohydrate-total nitrogen
ratio that is significant in determining the type of growth. Strongly vegetative
unfruitful plants were secured under conditions resulting in a high proportion
of insoluble nitrogen to carbohydrates. These conditions were a short day
and a good nitrate supply. If the nitrogen supply was kept up and the day
lengthened, conditions were present for the formation of an abundance of
insoluble nitrogen and also of carbohydrates. The result was strongly vegetative and fruitful plants. Conditions of long day and low nitrate supply
resulted in a high proportion of carbohydrate to insoluble nitrogen and a weakly
vegetative and unfruitful plants. Buckwheat, soy beans, radish, and Salvia
seemed to require a certain duration of light as well as a supply of carbohydrates for the synthesis of nitrates to insoluble nitrogen. This was not true
4 LEWIS,F. T., The typical shape of polyhedral cells in vegetable parenchyma
and the restoration of that shape following cell division. Proc. Amer. Acad. Arts and
Sci. 58: 53 7-55 2. IQ23.5 NIGHTINGALE, G. T., Light in relation to the growth and chemical composition
of some horticultural plants. Proc. Amer. Soc. Hort. Science I922: i8-29.