Cell Structure, Growth and Division in the Antheridia of Polytrichum etc. 149 
increasing thickness. So far as I have observed, no change appears in 
their staining reactions; but throughout the period now under discussion, 
as during the earlier history of the antheridium, the walls show a decided 
affinity for Congo red, and in the triple stain for orange G; although in 
the latter case the walls may at any stage be stained blue rather than 
orange by varying the time of exposure to the respective stains. 
During the history of the androcyte mother cells, too, there is a grow- 
ing tendeney for their plasma membranes, at least in fixed material, to 
draw away in places from the wall (PL VIII, Figs. 67, 70, 83 ; PI. IX, Figs. 98, 
121). This may be due to an increased susceptibility to plasmolysis at 
this period; but it seems likely that it is in part the first indication of a 
tendeney toward contraction which manifests itself to a greater degree 
in the androcytes, after their formation and previous to their metamor- 
phosis (PI. IX, Figs. 123 — 125). This contraction has for its final result — 
apparent in living as well as in fixed material — that the mass of androcytes 
occupies considerably less space within the antheridium than did their 
mother cells, even after making allowance for the space left by the dis- 
appearance of the partition walls. 
The contraction and partial rounding of the androcyte mother cells 
as the dissolution of their walls proceeds, recalls Miyake’s (1905) description 
of the corresponding stages in the history of the antheridia of Makinoa, 
when the androcyte mother cells “assume a more or less spherical form 
somewhat like the pollen mother cells of many flowering plants”. A 
similar contraction and rounding of the androcyte mother cells, accom- 
panied by a swelling of the walls, is observed by Wilson (1911) in Pellia 
and Aneura. Oddly enough, Wilson reports no shrinkage or rounding 
of the cells in the antheridia of Mnium or of Atrichum until after the final 
division, agreeing in this respect with the account given by the Leeuwen- 
Reijnvaans (1907 V) for Polytrichum. Their failure to observe these 
fairly conspicuous changes previous to and during the division of the 
androcyte mother cells suggests that possibly these authors have not 
actually seen this particular division in the musci which they studied. 
I have not found in the androcyte mother cells any structures which 
can be certainly identified with the kinetosomes of the immediately pre- 
ceding generations. There are, to be sure, occasional — sometimes fairly 
numerous — small, dark-staining bodies or granulös in the cytoplasm 
(PL VIII, Fig. 74); and it is not impossible that they, or some of them, 
are the remains of the formerly conspicuous kinetosomes, whose total 
bulk, as we have seen, has been progressively diminishing during successive 
cell generations. If this be the case, however, the granules remaining 
