4+ 
those colors that have the greatest illuminating power are those that 
least favor germination. 
Ad. Brongniart (1832) announced as the results of his experiments 
that the retarding influence of light depends not only on the illumi- 
nating power of the colored light, but on the relative quantity of white 
light that passes through the different colored glasses. In all these 
experiments the seeds were several millimeters below the surface of 
the soil, so that the colored lights did not affect the seeds directly, but 
indirectly through the soil whose temperature and moisture and 
evaporation may easily be of predominating importance. _ 
Ph. A. Pieper (1834), Meyen (1837), Zantedeschi (1846), and 
Belhomme (1854) have all experimented on the growth of seeds 
under colored glasses; but the sources of error incident to this 
method of observation prevent us from drawing any conclusion as to 
the influence of light itself. 
Ville (1865) says that the injurious effect of solar radiation on 
germination is the result of the heat only and that the effect of the 
light is nappreciable. For aquatic plants whose seeds germinate in 
the water, darkness seems decidedly favorable to germination, but it 
acts only in an indirect manner by preventing the warming of the 
water and the disengagement of the oxygen that is dissolved in this 
water. 
Charles Darwin (1877) says that certain species of seeds do not 
grow well when they are exposed to the light, even the diffuse hight of 
a room. 
Duchartre (1877) considers the action of darkness as a secondary 
influence, useful but not at all essential and concerning which there 
has been too much exaggeration. 
Faivre (1879) has shown that the appearance of the primordial 
latex occurs at a moment when the radicle is only a few millimeters 
long and when the cotyledons are still inclosed in the seed envelopes 
and have not yet received the action of hght. He notes that under : 
yellow light obtained by transmitting sunlight through a solution of 
bichromate of potash the seeds develop their chlorophyl and their 
latex more rapidly, and consequently have a shorter period of ger- 
mination than under a blue light obtained by transmitting sunlight 
through a solution of the ammoniacal oxide of copper. 
Detmer (1880) has consecrated an extensive work to the study of 
the germination of seeds, and states that concerning the action of 
light we are still ignorant as to whether it is direct—that is to say, 
whether it stimulates the storing up of new substances in the vege- 
table tissue or whether, on the contrary, it strengthens the persist- 
ence within the cells of some special process having a more or less 
intimate relation to the phenomena of growth and which can only 
