ON THE INFLUENCE OF SOLAR RADIATION ON PLANTS. 383 
stunted roots from the peas, while under the other a thick crop of green 
spreading plants arose from the germinating peas, but the wheat-plants were 
few, straggling, and unhealthy in appearance. When, however, we come to 
look more closely into the phenomena, we see certain points of resemblance. 
In both cases the cutting off of the chemical rny facilitates in a marked * 
manner the process of germination, and that both in reference to the protru¬ 
sion of die radicles and the evolution of the plume. The unnaturally tall 
growth of the stem, and the poor development of leaves in darkness, more or 
less complete, is also common to both these specimens of the monocotyle- 
donous and dicotyledonous plant. In both cases too, the yellow ray exerted 
a repellent influence upon the roots, giving the wheat a downward and the 
pea roots a lateral impulse. 
The object of employing a partially obscured yellow glass in these experi¬ 
ments, was to decide if possible the question which has been asked, Does yellow 
light stop germination by some specific action or merely by the excess ot light? 
Contrary to the experience of some others, who, 1 believe, have experimented 
on seeds covered with soil, and on other plants than those employed by me, 
d>e yellow light did not interfere at all with germination, in the experiments 
just described. In the case of both plants, indeed, it decidedly facilitated the 
early development of both the root and the plume. That the yellow ray, 
however, has a specific action of its own, is proved by the most cursory 
Ranee at the facts already recorded; the yellow and the obscured yellow 
give quite different results from those of any of the other glasses. 
he diversity between the effect of the same qualities of light upon the 
growth the wheat and the pea leads us to suspect at once any gencralisa- 
- tu affecting other nlnnta ivliioli It,MV h« rimwn from the observed influence 
UUI r\, UllU Hi t*MVr . I 1 
le third and fourteenth days. At the former period ne 
ie red the plant had attained 4\> times its original size, 
