ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
53 
Action of Cold and Sunlight on Aquatic Plants.* * * § — Dr. A. J. Ewart 
replies to the criticisms of W. and G. S. West on his previous publica- 
tion on the action of cold on aquatic plants. Certain algae (though 
not all) are very sensitive to a depression of temperature to near the 
freezing point; and this is especially the case with cells in a motile 
condition. It is probable that no purely aquatic fresh- water plant can 
withstand complete freezing when in an actively vegetating condition. 
It is certain that intense illumination acts injuriously upon all exposed 
living parts of plants, and not only on the cells containing chlorophyll, 
although these are first affected. In living chloroplastids exposed to 
light, the decomposition and reconstruction of chlorophyll proceed 
simultaneously, and in certain cases the total amount formed in a 
single day may be several times greater than that present at any given 
moment. 
Assimilation.f — Prof. C. E. Barnes objects to the term assimilation 
for the process of manufacture of carbohydrate foods, and proposes the 
general adoption of either one of two terms that have been suggested, — 
“ photosynthesis ” or “ phototaxis.” Assimilation might then be reserved 
for the repairing of waste and for the formation of new parts. 
Absorption of Carbohydrates by Roots.J — From experiments made 
on the cultivation of wheat, maize, pea, and other plants, M. J. Laurent 
concludes that, in most green plants there are probably two modes in 
which carbon is assimilated, — the chlorophyll-function, and the absorp- 
tion of certain organic compounds after digestion by the root. The 
mode of nutrition of non-chloropliyllaceous plants is only a particular 
case of that of green plants in general. 
Chlorophyll-assimilation of Littoral Plants.§ — From observations 
made on a variety of plants growing on the sea-shore, M. E. Griffon 
concludes that in the leaves of maritime plants a reduction of the 
amount of chlorophyll takes place under the influence of the sodium 
chloride, while the leaves and stems acquire a greater thickness and a 
larger development of the assimilating tissues. This increase, however, 
does not neutralise the injurious effects of the sodium chloride, the 
assimilation calculated for a unit of surface being always reduced. 
Action of Chloroform on Carbon dioxide Assimilation. || — From 
experiments on Elodea canadensis , Dr. A. J. Ewart confirms the state- 
ment that chloroformed water-plants cease to evolve bubbles of oxygen 
in the light, but recover this power immediately if the chlorophyll be 
at once removed. After immersion for five minutes the plant loses the 
power of recovery. With a more dilute solution, the power of recovery 
is not lost even after a longer immersion. 
C3) Irritability. 
Action of External Irritation on Plants.^ — The shoots of Cucur- 
bita Pepo display strongly marked plagiotropism. Herr F. Czapek has 
* Ann. of Bot.. xii. (1898) pp. 363-97. Cf. this Journal, 1898, p. 453. 
t Bot. Centralb]., lxxvi. (1898) pp. 257-9. 
J Comptes Kendus, cxxvii. (1898) pp. 786-7. Cf. this Journal, 1898, p. 101. 
§ Tom. cit., pp. 449-52. [| Ann. of Bot., xii. (1898) pp. 415-7. 
*[[ Flora, lxxxv. (1898) pp. 424-38 (1 pi., 3 figs.). 
