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Charles E. Allen 
(1907), except for the last division in botli genera, and by Wilson (1910, 
1911) for all the antheridial divisions in Mnium , as well as in Atrichum. 
Ikeno (1904) finds no centrosomes in the earlier androgonial mitoses of 
Atrichum or of Pogonatum. 
In the light of these conflicting and mostly fragmentary accounts, 
it is too early to form an opinion as to how generally a polarity of cell 
Organization prevails arnong the bryophytes. There appears, to be sure, 
at least in the hepaticae, a rather widespread tendency toward the occur- 
reuce during mitosis of a well-defincd aster at each spindle pole; but it 
has not been shown that the two result from the division of a single aster, 
so that their presence is no proof of the permanent polarity of the cell. 
Nor is there any satisfactory evidence of the existence in any bryophyte 
of a definite, persistent centrosome-like body — the blepharoplast, of 
course, excepted. 
On the other hand, the present study has shown that the cells which 
make up the interior of the antheridium of Polytrichum are marked by 
a condition of polarity which persists throughout the life of each cell and 
is transmitted through a long series of cell generations. Such a polarity 
characterizes the first-formed androgones and all of their descendants, 
down to and including the antherozoids. This type of Organization is 
manifested in the cells of different generations by the appearance and 
activitv of very different structures, all located in the cytoplasm. Except 
during mitosis and the stages just precedent and subsequent thereto, 
I have found no trace of a polar arrangement of the nuclear structures. 
In this respect, the nuclei seem to be very different from the permanently 
polarized nuclei of certain ascomycetes (Harper, 1897, 1905), but they 
resemble, so far as present available evidence shows, the nuclei of other 
bryophytes and of the plants of higher groups. 
My preparations afford no evidence of a permanent polar Organiza- 
tion of any of the vegetative cells in the neighborhood of the stem apex, 
in the leaf primordia, or in the wall cells of the antheridia. Negative 
evidence, of course, is by no means conclusive on this point; for the polarity 
of the androgones and androcytes is recognizable only because of the 
presence of certain specially-stained structures, and it is not to be imagined 
that the position and bchavior of these conspicuous structures are the 
only factors involvcd in the Organization of the cell. It would be sur- 
prising, indeed, ultimately to discover, although it is not inconceivable, 
that the cells within the antheridia of Polytrichum differ in their mode 
of Organization from all the others which constitute the plant. 
Only further extended investigations can determine whether there is 
