ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
227 
infloresconce of Daucus Carota , &c. It is usually associated with a 
peculiar odour, and is connected with the attraction of certain insects 
which are useful for the pollination of the species, and the repulsion of 
others. 
(2) Nutrition and Growth (including- Germination, and Movements of 
Fluids). 
Influence of Light on the Propagation of Plants. 5 " — Dr. G. Klebs 
discusses this subject in detail, especially in reference to the non-sexual 
propagation of the lower plants. 
In some Algae, as Chlorococcum infusionum and Ulothrix zonata , light 
has very little or no influence on the formation of the swarmspores, 
acting only through the stimulus to nutrition. In Vaucheria and Hydro- 
dictyon reticulatum the favourable effect of light on the production of 
swarmspores is much more evident ; in the latter case especially the in- 
fluence of light is apparently direct. 
In those Mosses in which the product of germination of the spore is 
an algoid filiform protoneme — e. g. Funaria hygrometrica — the formation 
of buds on the protoneme is essentially dependent on light ; if light is 
excluded, the protoneme continues to grow without producing buds, a 
phenomenon which the author compares to the production of Chantransia 
from Batrachospermum in the dark. When, however, a protoneme is 
developed from a cut leaf of Funaria, it forms buds in the dark much 
more readily than does a protoneme resulting from a spore. The sub- 
stances required for the formation of the bud are probably already 
present in the leaf. The germination of the spores of the Hepaticse is 
also dependent on light, as is likewise the production of the sexual 
organs on the prothallium of ferns. 
In sexual reproduction the processes are much more complicated. In 
the majority of Algas light is an important factor in the production of 
sexual organs. This is remarkably the case with the formation of 
these organs in Vaucheria and (Edogonium, with the process of conjugation 
in Spirogyra, Closterium, and Cosmarium , and with the production of the 
female organs in the Hepaticae and Musci. 
As respects Flowering Plants the statements of different observers 
with regard to the influence of light on growth appear at first sight to 
be at variance with one another. According to the researches of Sachs, | 
the leaves contain all the substances necessary for the formation of 
flowers, which can, therefore, be developed in the dark. The ultra- 
violet rays are especially effective in the production of the sexual 
organs ; and with algae the blue-violet half of the spectrum is much 
m'ore efficient for this purpose than the red-yellow half. Parasites 
destitute of chlorophyll can develope flowers in perfect darkness. 
Influence of Light on Flowers.j: — Dr. H. Vochting discusses the 
influence of light on the form and position of flowers. Experiments on 
the growth of a great variety of species under different degrees of illu- 
mination showed that a minimum of illumination is essential for the 
* Biol. Centralbl., xiii. (1893) pp. 641-56. f Cf. this Journal, 1892, p. 510. 
t Jahrb. f. wiss. Bot. (Pringsheim), xxv. (1893) pp. 149-208 (3 pis.) Cf. this 
Journal, 1887, p. 266. 
