338 BOTANICAL GAZETTE [NOVEMBER 
spores, I do not venture even to guess. On this interesting point I 
have no data. 
It.may be that in addition to the influence of light on the processes 
of food manufacture and growth in the spores and in cells adjacent 
to the sporangia, there are irritable responses which contribute to the 
development of the mechanical pressure which causes the spores to be 
discharged. Information on this point might add to our meager 
knowledge of the phenomena of irritability in the marine algae. 
I am by no means satisfied that the plant does not irritably respond 
to the light by more immediate means than growth. The light may 
also favor gelatinization, but the connection with this process, the 
details of which are unknown, is not sufficiently clear to justify 
discussion now. . 
The influence of light upon the germination of the spores.—The 
germination of the spores of Dictyopteris has been adequately 
described by REINKE (17), but he naturally made no attempt to 
ascertain the influence of the different factors of the environment 
upon the course of germination and upon the form of the young 
plants. In order to learn something about these matters I compared 
spores which had escaped during twenty-four hours in different dishes 
as to their rate of germination and the development of the young 
plants in the light and in darkness. In jig. 13 we have young plants 
shown which had developed thus far in a dish completely covered by 
black paper except for a vertical slit 17 x6™™ on the side of the dist 
toward the window. The time since sowing was three and three- 
quarters days. In fig. 14 are shown young plants from spores est 
at the same time, but in dishes kept completely 
be objected that the conditions of the two experiments were not U 
same, and therefore the results may not be comparable. i - 
shown above that light favors the escape of the spores, si 
because it favors their growth. For this reason, therefore, the res" 
are exactly comparable, because the point is made still clearer © 
the germination of the spores is more rapid under the normal 
alternation of light and darkness than in continuous 
the germination of the spores of ferns (4, P- 423-4 
Viscum, and for various other plants it is claimed that 
sary. This is not generally the case with higher plants. 
), the seeds 
light is nect* 
darkened. It may 
darkness. i 
