542 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
Effect of Currents of Water on Assimilation.* * * § — As the result of a 
series of experiments on aquatic plants ( Anacharis , Hottonia , Potamc- 
getori ), Mr. F. Darwin and Miss D. F. M. Pertz find that the energy of 
assimilation, as shown by the number of hubbies of gas formed, is 
. greatly increased by the setting up of currents in the water, thus bring- 
ing the leaves rapidly into contact with fresh layers of water. It is to 
this cause, and not to any physical stimulation, that the increased activity 
is due when a small proportion of alcohol is added to the water. 
Respiration and Assimilation.f — From experiments made in passing 
a current of hydrogen through water containing a vigorous leaf of Elodea , 
Prof. J. B. Farmer comes to the conclusion that, as fast as the carbon 
dioxide is produced as the result of respiration, it is split up, and the 
oxygen liberated by the granules of chlorophyll under the influence 
of daylight, and thus rendered available for purposes of continued 
respiration. 
Relation between Respiration and Nitrogenous Substances.^ — 
According to Herr W. Palladine, there is a constant relationship between 
the amount of carbon dioxide exhaled by plants and the amount of pro- 
teinaceous substances which they contain. If the former is represented 
CO 
by C0 2 , and the latter by N, then the value of the fraction is con- 
stant, subject only to accidental variations due to secondary causes. In- 
other words, protoplasm possesses in all plants the same energy. Subject 
to the variations already mentioned, the cell disengages the same amount 
at different stages of its growth. The experiments on which these state- 
ments were founded were made mostly on wheat. 
Role of Osmose in Transpiration^ — Mr. H. H. Dixon gives further 
evidence in favour of his view that transpiration from the leaves is the 
primary factor in the ascent of sap in the plant. The arrangement in 
the leaf is a beautiful automatic contrivance by which, in times of exces- 
sive evaporation, the osmotic power of the cell is increased by the greater 
concentration of the sap contained in it. In addition to the tension 
set up by the osmotic cells of the leaves in the water-conducting system 
of plants, it seems probable that, under all circumstances, the cells of 
the medullary rays must draw the water needed in their metabolism 
from the water-conduits by their osmotic properties. 
(3) Irritability. 
Physiology of Tendrils.|j — Herr C. Correns states that a gradual 
rise of temperature up to about 40° C. has the same effect on tendrils 
(Passiflora, Cucurbita , &c.) in causing curvature as contact irritation, the 
reaction beginning at the apex when the warming is uniform over the 
whole tendril. A gradual cooling has also the same effect, as also has 
chemical irritation. 
* Proc. Cambridge Phil. Soc., ix. (1896) pp. 76-90. 
t Ann. Bot., x. (1896) pp. 285-9. 
X Rev. Gen. de Bot. (Bonnier), viii. (1896) pp. 225-48 (3 figs.). 
§ Proc. R. Irish Academy, iii. (1896) pp. 707-75 (1 fig.). Cf. this Journal, ante , 
p 88. 
|| Bot. Ztg., liv. (1896) pp. 1-20, and Bot. Centralbl., lxvi. (1S96) pp. 290-1. 
