38 
True, Notes on thePliysiology of tlie Sporophyte etc. 
sporopliytes performed this reaction, indicating tliat for a time, 
tlie young sporopliytes are not very sensitive to light, becommg 
increasingly so until tliey react tlirongh a distinct cliange in tlie 
distribution of growth, resnlting in tlie inclination seen. 
A Mnium cnlture in which only erect sporopliytes were seen 
•was placed on April 11, at 12 : 00 m, in a horizontal position 
and illnminated witli light reflected from the sky in a direction 
parallel with the long axes of the sporopliytes. After 20 hours 
several showed slight bends near the tips, in diffeient dnections, 
some npwards, two laterally, others downwards. On April 13, 
hve out of twenty-two individuals were inchned downwards, 
three npwards, two laterally, tlie remainder maintaining the ho¬ 
rizontal position, presumably not yet having reached tliat stage 
in their development at which tliey became sensitive to gravity. 
On April 16, eight showed a downward curvature, three pointed 
oblicptely downward, two pointed upward, nine were still hori¬ 
zontal. ' Tliree had bec'ome capable of perception and motion 
since April 13, and had responded by a downward curvature. 
On April 17, ten curved downward, "tlie two laterally directed 
individuals liad changed position so as to point downward, two 
still pointed upward. On April 19, all had taken a position in 
which the sporopliytes pointed downward. 
From this Experiment, it appears tliat for a time tlie young 
sporopliytes are not perceptive to gravity and maintam for dat s 
in a horizontal position an „Eigenrichtung" derived possiblv 
from the relation to the sporophyte. As they become capable 
of perception■ and reaction, in spite of Illumination parallel witli 
their long axes, the rudiments respond by curvatures directing 
the apices toward the earth. 
Thus it appears probable tliat Mnium sporopliytes take on* 
the curvature characteristically in ade in response to geotropie 
induction. 
In the hope of getting further light on the question of the 
part played by gravitation and light, a culture of Mnium was 
placed in a perpendicular position, illuminated from above b\ 
dif'fused light. 
On April 12, all sporopliytes were perpendicular, on April 
13, thirteen out of thirty showed a distinct curvature near the 
base of the calyptra. Ön April 15, hfteen w^ere still erect, the 
others showing curvatures varying from a hwv degrees to as high 
as 90 o from the perpendicular. On April 18, all were more or 
less inclined, and in various radii, indicating no niarked directive 
influence. Here, as bevore, a period of inability to perceive or 
react is followed by perception and reaction. 
From tlie experiments sketched here in scant outline, it ap¬ 
pears probable tliat the curvature of the seta in the species is 
due to a growth reaction on the part of the young sporophyte 
to the Stimulus of gravity. It appears probable, also, in view 
