ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
89 
(3) Irritability. 
Mechanics of Curvature-Movements.* * * § — Dr. F. Noll controverts the 
view taken by Kohl, that the phenomena of curvature are due to an active 
shortening of the concave, and a consequent passive lengthening of the 
convex side of the organ in question. The observed phenomena show, 
on the contrary, that the convex membrane is subject to greater elastic 
and plastic tension than the membrane of the concave side, which is 
affected in the ojjposite direction. He does not agree with Pfeffer that 
the phenomena of tension point to a growth by intussusception. The 
author suggests that the transformation of the elastic tension into a 
plastic change of form may be due to the excretion from the protoplasm 
of one or more substances which produce an effect similar to that of 
sulphur in the vulcanising of caoutchouc. 
Transmission of Irritation in Mimosa.f — Mr. D. T. MacDougal 
claims to have proved that the transmission of the stimulus in Mimosa 
pudica does not take place through the vesicular cells, but, in all pro- 
bability, through the tissues of the entire cross section. 
Geotropism of Roots.J — M. M. Wachtel replies to Sapoznikow’s 
defence of Knight and Hofmeister’s theory that the downward geotropic 
curvature of roots is a purely passive phenomenon. By a series of 
experiments with an apparatus specially contrived for the purpose he 
demonstrates the active character of the curvature, and of the considerable 
expenditure of force that takes place in it. 
Plagiotropic Position of Lateral Roots.§ — Herr F. Czapek contests 
Sachs’s theory that the plagiotropic or oblique direction of growth nor- 
mally assumed by lateral roots is due to their being endowed with a 
weaker positive geotropism than is the case with the primary root. He 
suggests, on the other hand, that it is the result of the mutual action of 
positive geotropism and of a second kind of geotropism which tends to 
cause the roots to assume a horizontal direction. 
(4) Chemical Changes (including 1 Respiration and Fermentation!. 
Digestion of Gelatinous Endosperm || — M. Leclerc du Sablon has 
studied the processes which take place in the absorption of the endo- 
sperm in those Leguminosse — e. g. Gleditschia, Sophora — where the reserve 
focd-material is formed from the thick gelatinous cell-walls. They 
consist almost entirely of carbohydrates. The seeds were found to 
contain a diastase which at all events takes a share in the digestion of 
the reserve substances. The principal product of digestion is a carbo- 
hydrate analogous to dextrin ; this is absorbed by the plant, and appears 
to be assimilated directly. The glucose which is produced in small 
quantities in the endosperm, and which does not exist in the seedling, 
plays a secondary part in germination. Saccharose, which is abundant 
* Flora, Ixxxi. (1S95), Erg'anz.-Bd., pp. 36-87 (3 figs.). Cf. this Journal, 1895, 
p. 455. f Bot. Gazette, xx. (1895) pp. 411-2. 
% Arb. St. Petersb. Naturf. Gesell., xxv. (1895) 17 pp. and 1 pi. See Bot. Cen- 
tralbl., lxiii.(1895) p. 309. Cf. this Journal, 1888, p. 458. 
§ Ber. Deutsch. Bot. Gesell., xiii. (1895) pp. 299-302. 
|| Rev. Ge'n. de Bot. (Bonnier), vii. (189.5) pp. 401-8. 
