—81 — 
sufficiently for the fixing solution. The involucres for the most part 
are tightly closed over the young embryos, but as soon as they are 
put into the liquid they lift up enough to form a bubble which pre- 
vents fixation. This makes very careful trimming necessary for this 
part of the plant. 
Much of the material collected Aug. 6 closely resembled that 
gathered on Aug. 2 and July 26, shown in fig. 35, but the more ad- 
vanced stages now show a decided development. Fig. 36 shows that 
the cells in the young embryo have begun to differentiate into the 
archesporial cells and around the outside of these are two definite 
rows of ceils which will form the capsule wall. The archesporial 
cells show plainly for the protoplasm is denser and they take a deeper 
stain. Development in the walls of the venter now seems to have 
come to an end. 
Some of the sections from material collected Aug. 9 seem to show 
an increase in the size of the embryo, it being somewhat longer and 
showing a slight tendency toward a differentiation in shape between 
the rectangular and more compact cells in the region of the seta and 
those lower down in the region of the foot, the latter being longer 
and looser in structure. 
Several sections of material collected Aug. 15 indicate that there 
are two kinds of cells in the archesporial region, those more nearly 
round or rectangular with large nuclei and which will become spore 
mother cells and others somewhat elongated which will develop into 
elaters (fig. 37). 
[to be continued] 
i — involucre, ar — archegonia. an — antheridia. 
Fig. 27a. Long, section through thallus X 55, Growing on very 
wet soil June 14. i — involucre, ar — archegonia. 
Fig. 28. Another part of long, section through end of thallus repre- 
sented in fig. 26 X 233. 
Fig. 29a. Involucre and most of surrounding tissues dissected away 
to show grouping of archegonia near end of thallus X 40. 
Coll. Aug. 17. 
Fig. 29. Median, longitudinal section through growing point of 
thallus, X 55. coll, Apr. 21. Shows 4 stages of antheridia 
from immature one nearest tip to one fully developed farthest 
from tip. 
Fig. 30. Median longitudinal section through growing point of thal- 
lus X 233. June 14. Same as fig. 25, only more highly mag- 
nified. 
Fig. 31. Longitudinal section through antheridium in another part 
of same thallus X 233. June 14. 
(Fig. 32 of Miss Greenwood is omitted). 
