ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
389 
A. ornithocephala about 6000, pollen-grains are required for the complete 
fertilization of the ovary. Out of a very large number of observations 
made on flies captured in the chamber of A. barbata and elegans, only 
a very few showed the presence of even a small number of pollen- 
grains adhering to them. On the other hand all three species are 
abundantly fertile when pollinated with their owii pollen. 
From these observations Herr Burck concludes that the various 
species of Aristolochia are self-pollinated without any assistance from 
insects. 
(2) Nutrition and Growth (including Germination, and Movements 
of Fluids). 
Right-angled Succession of Cell-walls.* * * § — Prof. J. Sachs recurs to his 
theory on the relation between growth and cell-division, viz. that in the 
growth of vegetable tissues the direction of the successive division-walls 
is at right angles to one another, whether periclinal, anticlinal, or 
transverse. The walls may themselves be curved, but at the point of 
intersection the angle is a right one. Prof. Sachs suggests that this law 
is as applicable to the animal as it is to the vegetable kingdom. 
Dissemination of the Seeds of Geranium bohemicum.| — Dr. Lund- 
sirotn points out that the mode of bursting of the fruit in Geranium 
bohemicum differs from that in G. sylvaticum and other species. Instead 
of the mericarps separating from below and remaining for a time attached 
to the upper part of the column, they separate from above and remain 
buried in the calyx. Their dissemination cannot therefore be effected, 
as in other species of Geranium and Erodium, by the elasticity of the 
portion which remains attached to the central column. This upper part 
of each carpel, which remains attached to the seed, is, in G. bohemicum , 
spirally twisted, and its dissemination appears to be effected by its 
becoming attached to the fur or wool of creeping animals, or to the 
feathers of birds. 
Germination of Bupleurum aureum.| — M. P. Van Tieghem describes 
a peculiar mode of germination in Bupleurum aureum. from Siberia, which 
has been observed in some other Umbellifene, and in a few other plants. 
The two cotyledons have their petioles concrescent by their edges so as 
to form a tube. This cotyledonary tube is negatively geotropic in its 
upper portion, causing it to ascend vertically, while its lower part is 
positively geotropic, and strikes into the soil. It follows from this that 
geotropic characters cannot be used to determine the morphological value 
of an organ. 
Autumn and Spring Flowering Plants. §— Herr A. F. Foerste advo- 
cates the view that the normal time for the flowering of plants is the late 
spring and early summer. In the struggle for existence two opposite 
tendencies have set in : — The one is to obtain advantage over surrounding 
plants by increasing in size, and thus securiug more air, light, and room 
* Flora, lxxv. (1892) pp. 63-7. 
t Bot. Sekt. Naturv. Students'allsk. Upsala, Feb. 28, 1890. See Bot. Centralbl. 
xlix. (1892) pp. 202 and 236 (9 figs.). 
t Bull. Soc. Bot. France, xxxviii. (1891) pp. 402-3. 
§ Bot. Gazette, xvii, (1892) pp. 1-8 (2 pis.). 
