True. Notes on the Physiology of the Sporophyte etc. 
37 
tliat in all stages of growtli open to study this was true. Ac- 
cordingly, to more accurately define this zone, it was necessarv 
te remove the calyptra, After a number of failures due to the 
great delicacy of the tissues in the end of the young sporophyte, 
it was foünd possible to remove this structure and fix dots of 
India ink at close intervals along the apical region. Measure- 
ments rnade at intervals of twentv-four hours thereafter showed 
tliat the zone of elongation was limited to a space within 2 mm 
from the apex, most rapid growth being found about 0.8 mm 
from the tip. The young seta was found to have reached its 
complete diameter at any given point as soon as its growth 
in lengtli was completed. The diameter near the base 
averages about 0,15 mm and about 0.14 mm near the base of 
the capsule. 
In a number of young sporopliytes from which the calvp- 
trae liad beeil removed, sharp curvatures appeared, resembling 
verv strongly the träumatropic curves seen in roots (4). These 
curvatures were probably due to sliglit unavoidable injuries in- 
fiicted in removing the calvptrae. To slightly inflict a wound 
near the apex was found to produce similar results in erect spo- 
rophvtes from which the calyptrae had been successfully remo¬ 
ved. Decapitation experiments seemed to show that the percep- 
tive region lies in the immediate apex of the sporophyte. 
Having traced roughly the course of the elongation of the 
sporophyte and its distribution as seen in Funarm. attention was 
directed toward determining the influences bringing about the 
well - known curvature of the seta seen in Funaria and of 
Mnium. 
3fniiim showed itself very sensitive to conditions of light in 
its natural habitat as indicated by the uniformity with which 
the individual sporopliytes of a turf assume their positions with 
regard to their environment. Since Funaria shows itself to be 
less acuratelv directed. Mnium was selected for these experiments. 
Pot cultures Avere exposed in various positions to the action of 
gravity and light in the liope of ascertaining whether light is 
the sole directive influence, as indicated by AVicliura. 
On April 11 at 11 : 45 a, m. a pot of Mnium having 30 young, 
erect sporopliytes was placed in a dark box in such a manner 
that the perpendieular sporophytes were subjected to lateral illu- 
mination through a hole two inches wide by four inches long 
at the level of the culture. The pox Avas placed near a soutli 
window in strong diffused light. 
Twenty-four hours later, eight of the sporophytes AA^ere in- 
clined about 20 o from the perdendicular toward the source of 
light, by means of a bend within or at the base of the ea¬ 
lyptra, 
After another twenty-four hours, fifteen individuals liad made 
similar curves toAAmrd the light. On April 16, about 120 hours 
from the beginning of the experiment, all but three shoAA T ed plain 
inclinatioih It Avas noted that in eAmiw case, the more adAmnced 
