ZOOLOGY AND BOTANY, MICROSCOPY, ETC, 
455 
epiderm is not essential for the production of geotropism, while both the 
pith and the peripheral parenchymatous tissue appear to play an essen- 
tial part in it. 
Influence of Contact and Traction on Twining Leaf-stalks.* — 
Herr M. von Derschau recalls the fact that contact causes in twining 
leaf-stalks a more or less pronounced increase in thickness, and a 
mechanical strengthening. These results are the greatest when the 
vascular bundles have a crescent-shaped arrangement, since the vascular 
bundle-ring is then closed. When the weight is small traction affects 
a twining leaf-stalk in the same way as contact, while with a heavier 
weight the effect is the reverse. The observations were made chiefly on 
plants belonging to the Solanacese, Scropliulariacese, Ranunculacese, and 
Tropaeoleae. In some cases the upper, in others the under side of the 
leaf-stalk w*as found to be the most sensitive. Light falling on one side 
retards the twining. The leaf-stalks of Lophospermum scandens are 
especially heliotropic. 
Mechanics of Irritation-Curvatures. f — Herr G. F. Kohl explains 
the phenomena of irritation as simply turgor-curvatures, which become 
subsequently fixed by growth, due to the fact that the concave side of 
the organ in question contains a larger quantity of osmotic substances 
than the convex side, and therefore possesses a higher degree of tur- 
gid ity. The cells on the concave side are regarded by the author as the 
active ones in inducing the phenomenon. He contests on several points 
the conclusions of Wiesner, Noll, and Wortmann. 
(4) Chemical Changes (including Respiration and Fermentation). 
Amylo-chlorophyllous Phenomena.! — An extended series of obser- 
vations on the mode of formation of starch-grains and chlorophyll-bodies 
in the plant has led M. E. Belzung to the following general conclusions. 
The first process which takes place in the embryo is the formation of 
starch, the result of the activity of the protoplasm, the chlorophyll-body 
being a secondary formation. With few exceptions the chlorophyll- 
pigment is diffused through the protoplasm of the young embryo. The 
substratum of the future chlorophyll-body — leucite or plastid — is always 
fully formed by the time the seed arrives at maturity. The protoplasm 
has always a reticulate structure ; it is the protoplasm of the amyliferous 
vacuoles which constitutes the chromatophore or leucite. The starch- 
grains which are destined to constitute the reserve food-material in the 
ripe seed are an exception to this rule, and increase in the meshes where 
they are originally deposited. In proportion as the embryo becomes 
green, and the mass of green corpuscles more abundant, the starch- 
grains are resorbed ; they are a part of the material for building up the 
green chlorophyll-grains. 
In adult green organs, especially leaves, the starch-grains which are 
* ‘ Einfluss v. Contact u. Zug auf rankende Blattstiele/ Frankfurt-a.-M., 1894, 
36 pp. and 3 pis. See Bot. Centralbl., lxi. (1895) p. 433. 
t ‘Die Mechanik d. Reiz-kriimmungen/ Marburg, 1894. See Bot. Ztg., liii. 
(1895) 2 te Abt., p. 147. 
x Journ. de Bot. (Morot), ix. (1895) pp. 33-49, 61-72, 101-8, 134-53, 181-9 
(2 pis. and 2 figs.). Cf. this Journal, 1892 p. 57. 
