504 
SUMMARY OP CURRENT RESEARCHES RELATING TO 
(2) Nutrition and Growth (including- Germination, and Movements 
of Fluids). 
Effect of the Electric Light on Vegetation.* — As the result of a 
series of experiments Prof. E. Chodat states that the electric light 
promotes the germination of seeds, and the lengthening of leaves and 
stems ; the leaves, however, are not so well developed as those of plants 
not exposed to the electric light. Its effect, therefore, is analogous to 
that of prolonged darkness. On the movement of the leaves of Oxalis 
the electric light had no influence. 
Adaptations for Epiphytism.j — Herr E. Loew enumerates a number 
of plants, natives of northern Germany, which appear to be on the way 
to becoming epiphytic. He finds them to be specially characterized in 
two different ways : — In a large number there is a special adaptation for 
the dissemination of the seeds, either by the fruit being edible, and the 
seeds therefore passing into the excrements of birds or other animals, 
or by the fruit or seeds being furnished with a floating apparatus. In 
other cases the plant is especially adapted for the absorption of food- 
material from decaying vegetable substances by the possession of an 
abundant mycorhiza. 
Influence of the Seed on the Development of the Fruit.f — According 
to Herr A. Miiller-Thurgau, the reduction of the number of seeds in the 
grape from the normal number of four to three, two, or one, or their total 
suppression, is not due to the failure of pollination ; this causes the 
falling of the flower. It is the result of imperfect impregnation, the 
pollen-tubes either not reaching the oosphere, or not finding it in a 
condition for impregnation, the ovules having probably been imperfectly 
nourished. The growth of the berry stands in direct relation with the 
development of the seeds, the development of the flesh being dependent 
on the irritation caused either by the entrance of the pollen-tube or by 
the growth of the seed. When there is only one seed the flesh developes 
more strongly on the side on which the seed lies. The presence of seeds 
also lengthens the period of ripening. Similar results were obtained 
also with currants, apples, oranges, apricots, and peaches. 
(3) Irritability. 
Latent Irritability.§ — Prof. J. Sachs states that the well-known 
sensitive motions of the roots of epiphytes can be incited also in aerial 
roots by placing them in a condition where these movements can be 
brought into play. The irritability must therefore remain latent in all 
roots. He has proved experimentally that, while the primary root of 
a seedling possesses true positive geotropism by which it directs itself 
vertically downwards, the secondary roots have each a modified geo- 
tropism of their own, in consequence of which they assume a definite 
angle with the primary root. The tertiary roots again do not display 
geotropism of any kind, but spring from the secondary roots in all direc- 
tions. These facts were demonstrated by observations made on potatoes 
* Arch. Sci. Phys. et Nat., xxviii. (1893) pp. 478-81. Of. this Journal, ante, 
p. 66. t Abhandl. Bot. c Ver. Prov. Brandenburg, 1892, pp. 63-71. 
X J B. Deutsch-schweiz. Versuchsstat., 1892. See Bot. Centralbl., liv. (1893) 
p. 26. § Flora, lxxvii. (1893) pp. 1-15. 
