VoL. XIV 
No. 6 
THE BRYOLOGIST 
NOVEMBER 1911 
SOME STAGES IN THE DEVELOPMENT OF PELLIA 
EPIPHYLLA. -I 
(concluded) 
HELEN E. GREENWOOD. 
After this time collections were made Aug. 17, 18, 21 and 23, on 
the latter date two being made from widely separated localities. The 
most advanced stage of this group came from the collection of Aug. 
18 (fig. 38). Here the differentiation into spore mother cells and 
elater forming cells has proceeded still further. These cells seem to 
be surrounded by a reticulated protoplasm, the network showing 
more or less distinctly with a fairly low power. The only difference 
noted in that collected on the twenty-third was that there were more 
loose cells in the open space within the capsule and the difference be- 
tween the two kinds of cells was still more evident. 
On August 28, growth was found to have gone on so rapidly that 
with a low power magnifier the sporogonium seemed to be fully de- 
veloped into a stem and well rounded out capsule. Vertical sections 
(fig. z9) through this material show that the archesporial division 
has been completed, the spore mother cells with their large nuclei are 
separated from each other and from the much elongated young elaters 
with their correspondingly small nuclei. The difference between the 
stem and the foot is now well defined, the latter forming a pointed 
cap which overlaps the base of the seta. The spore mother cells are 
in general spherical but a few of the more advanced ones show a 
tendency to become lobed. 
Vertical sections through sporogonia collected September 3 show 
a decided development in the spore mother cells over those collected 
Aug. 28 (fig. 40). They have all become distinctly lobed (fig. 41 ) 
but are still much scattered, occupying comparatively little space 
within the capsule. The elaters on the other hand, have much the 
same appearance, still being distinctly nucleate with no signs of spiral 
thickenings on the wall. 
Sections through capsules collected on Sept. 16 show the lobed 
spore mother cells to be much crowded and these now occupy a 
proportionately large space in comparison to the elaters which are 
still nucleate. 
Material collected Sept. 25 and Oct. 18 presents very similar 
stages of development (fig. 43). In both, the spore mother cells 
have become conspicuously four-lobed, but these four lobes diverge 
The Sept. Bryologist was issued Sept. 15. 
