ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
543 
Prof. D. T. MacDougal * claims priority for the more important of 
these observations. 
Movements of Sensitive Leaves. f — Experiments made by Herr A. 
J. Schilling on the leaves of Mimosa pudica and other sensitive plants 
show that, by attaching weights to the leaves the elastic force of the leaf 
can be increased more than fourfold. Under the highest weight which 
the leaf could sustain, the cushion of the primary leaf-stalk remained as 
sensitive on its lower side as under ordinary conditions. 
Irritability of the Calyx and Stamens of Helianthemum poli- 
folinm.j; — M. J. Briquet describes the very remarkable phenomena in 
this plant. The sepals display a well-marked sensitiveness to light, 
closing the flower even during the passage of a cloud across the sun. 
The stamens are irritable only during the time that the flower is expanded, 
this phenomenon being exhibited by the whole of the filament. The 
cortical cells of the filament are connected with one another by fine 
threads of protoplasm. The curvature of the filament appears to be due 
to an escape of water on the concave side ; this water passes into the 
intercellular space, and there ensues immediately a difference between 
the turgidity of the cells on the concave and those on the convex side. 
The purpose of the irritability of the stamens seems to be closely 
connected with the carriage of the pollen by bees.§ 
Effect of Light on the Ueotropism of Stolons.|] — M. J. Briquet 
points out that there are in the genus Mentha two kinds of stolon, 
epigasous and hypogeeous. If the latter are exposed to light, they 
change their previous horizontal direction of growth, and bend upwards, 
at the same time becoming green ; they are transformed, in fact, into 
ordinary leafy aerial branches. Light has the effect of transforming 
diageotropism into epigeotropism. 
Diaheliotropism.H — Mr. A. J. Ewart instances the radial stems of 
Pellionia Daveauana as a very good example of a plant in which the 
radial stem exhibits well-marked diaheliotropic irritability. 
(4) Chemical Changes (including Respiration and Fermentation). 
Physiology of Coloured Leaves.** — Dr. E. Stahl has investigated, the 
purpose of the colouring matter of coloured leaves, for which he prefers 
the term erythrophyll rather than anthocyan. lie established, in the 
first place, that the colour is no protection against the attacks of insects 
or snails ; while rodents and ruminants, on the other hand, exhibit a 
preference for green leaves. Its main purpose appears to be to act in 
connection with transpiration. The absorption of the rays of light by 
erythrophyll is complementary to that by chlorophyll ; the absorption 
of the red rays is advantageous to the plant by raising its temperature. 
This elevation of temperature was determined by experiment. Erythro- 
phyll has for its function the assisting of the process of metastasis. It 
* Bot. Centralbl., lxvi. (1896) pp. 145-6. 
If Jenaisch. Zeitschr. f. Naturwiss., xxii. (1895) pp. 416-33. See Bot. Centralbl., 
Bcih., vi. (1896) p. 124. X Ann. Sci. Pliys. et Nat., i. (1896) pp. 248-60 (1 fig.). 
§ See also ante, p. 540. || Arch. Sci. Phys. et Nat., i. (1896) pp. 273-5. 
^ Ann. Bot., x. (1896) p. 294. 
** Ann. Jard. Bot. Buitenzorg. xiii. (1896) pp. 137-216 (2 pis.). 
