350 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
dilated at the summit, flat, concave, or convex at tlie discoid base, with 
or without a central projection, and separated or not from the cotyledon 
by a groove. 
Embryo of Grasses.* * * § — Dr. E. Bruns describes the structure of the 
embryo of a number of grasses, especially in reference to the presence or 
al sence of the epiblast, a sheathing structure frequently found in 
connection with the lower part of the scutellum ; he regards it as being, 
like the scutellum, a reduced leaf or cotyledon, but destitute of a 
vascular bundle. The presence or absence of the epiblast is not uni- 
formly even a tribal characteristic. It was absent in all species 
examined of the Maideae and Andropogonere, and present in all those 
examined of the Oryzeae, Agrostideae, and Aveneae ; but in the Paniceae, 
Phalarideae, Festuceae, and Hordeae, there are genera with and genera 
without, and in the genus Br achy podium even species with and species 
without an epiblast. 
Embryo of Petrosavia.'f — Mr. P. Groom has examined the structure 
of the embryo of this genus of parasitic Liliaceous plants from the East 
Indies. He finds it to be of excessively simple structure, consisting of 
a very small number of cells, in never more than two layers, and with 
scarcely any differentiation. 
Phyllotaxy.j; — After discussing the various theories that have been 
propounded to account for the different varieties of phyllotaxy, Herr K. 
Schumann points out that the arrangement of leaves in straight or 
spiral lines is intimately connected with the symmetrical or unsymmetri- 
cal development of the sheathing bases of the leaves, which make their 
appearance upon the growing point of the plant before the leaves do. 
This is the case in all Monocotyledons and in most Dicotyledons. This 
view is supported by a description of the phenomena in Adoxa and in 
the cohort Fluviales. 
Leaves of Alpine Plants.§ — Herr A. Wagner has investigated the 
structure of the leaves of a number of alpine plants (Dicotyledons) with 
reference to their adaptations to the conditions of climate, especially to 
the necessity of an increased activity of assimilation required by the 
greater intensity of the light, the short period of vegetation, and the 
reduced amount of carbon dioxide in the atmosphere. He finds these 
adaptations provided for by the increase in length or in number of the 
palisade-cells, by the looser structure of the mesophyll, by the very fre- 
quent occurrence of numerous stomates on the upper surface, and by the 
usually exposed position of the guard-cells. The leaves do not in 
general exhibit any provisions against excessive transpiration ; this is 
shown by the loose structure of the mesophyll, the absence of a strongly 
thickened epiderm, the exposure of the stomates, and the absence of any 
aquiferous tissue. These precautions are rendered needless by the great 
moisture both of the air and of the soil. They occur to the largest 
* Flora, lxxvi. (1892) Erganzungsband, pp. 1-33 (4 pis.). 
t Ann. Bot., vi. (1892) pp. 380-2 (1 fig ). 
X 4 Morpliologische Studirn,’ Iste Abtheil., Leipzig, 1892, 206 pp. and 6 pls ; 
See Amer. Journ. of Sci , xiv. (1893) p. 167. 
§ SB. K. Akad. Wiss. Wien, ci. (1892) pp. 487-518 (2 pis.). 
