ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
645 
purpose of these structures is obviously the regulation of the amount of 
water contained in the plant. 
Opening and Closing of Stomates * — According to Dr. F. G. Kohl, 
the guard-cells of the stomates generally possess a greater turgor than 
the other epidermal cells. An opening and closing of the stomates was 
observed in some plants where they have been hitherto regarded as 
functionless. Only in Salvinia natans were they found to bo entirely 
non-motile. Closed stomates, when treated with diastase, open and 
remain open under all conditions. The dark heat-rays have the same 
effect as light in causing an opening of the stomate. Of the light-rays, 
only the red and blue possess this power, apparently because they are 
the most readily absorbed by the chloroplasts. 
Floating Leaves.f — Herr E. Jahn formulates the following four 
structural conditions which enable leaves to float on the surface : — 
A low specific gravity (but not sufficiently low to interfere with the 
firmness of the leaf ) ; as large a surface as possible ; the fixing of the 
leaf-stalk as near as possible to the centre of the leaf (this is often se- 
cured by the cordate or peltate form of the leaf ) ; the great length 
of the leaf-stalk, which must be fixed to the lamina at a high angle. 
Epiderm of the Leaf of Grasses. J — From an examination of a very 
large number of species of Graminese, Dr. A. Grob distinguishes the 
following classes of elements in the epiderm of grasses : — (1) elongated 
epidermal cells ; (2) bast-shaped epidermal cells ; (3) transverse cells ; 
(4) vesicular cells ; (5) short silicified cells; (6) short cork-cells; (7) 
intermediate cells; (8) spiny hairs; (9) hooked hairs; (10) bristle- 
hairs ; (11) soft hairs ; (12) bieellular hairs bent at a right-angle ; (13) 
stomates (6-celled in Sesleria coerulea). The elongated epidermal cells, 
the short silicified cells, the short cork-cells, the unicellular spiny hairs, 
the bieellular bent hairs, and the 4-celled stomates of peculiar structure, 
are especially characteristic of the order. The extent to which these 
characters can be used in the classification of the species is pointed out. 
Leaves of Euphorbia buxifolia.§ — Prof. E. Warming describes the 
arrangement of the leaves in this species which present a remarkable 
example of anisophylly. They are opposite, and are arranged in two 
orthosticliies, a very unusual arrangement in Phanerogams. They are 
provided with small intrapetiolar stipules. Either only one leaf of each 
pair produces an axillary bud, or one of the buds is much more vigorous 
than the other. 
Production of Bulbils by Lachenalia and Hyacinthus. || — Herr H. 
Lindemuth states that stems of Lachenalia luteola and Hyacinthus orien- 
talis can be induced to produce bulbils even when entirely destitute of 
leaves, if cut off and placed in water. In Lachenalia they are of exo- 
genous origin, being derived from the epiderm and the underlying 
cortical layers. Adventitious roots of endogenous origin are also pro- 
duced, originating from the peripheral vascular bundles. In Hyacinthus 
* Bot. Beibk z. Leopoldina, 1895, 4 pp. See Bot. Centralbl., lx'vii. (1896) p. 52. 
f Beitr. z. wiss. Bot. (Fiinfstuck), i. (1896) pp. 281-94 (1 pi.). 
t Biblioth. Bot. (Luerssen u. Frank), Heft 23, 1896, 123 pp., 10 pis. and 1 fig. 
§ Overs. K. Danske Yidensk. Selsk. Forhandl., 1896, pp. 326-34 (2 figs.) (French). 
II Ber. Deutsch. Bot. Gesell., xiv. (1896) pp. 247-52 (2 figs.). 
1896 2 y 
