Cell Structure, Growth and Division in tlie Antheridia of Polytrichum etc. 177 
the androcyte mother cell, perhaps frora some of the very substance wliich 
in the androgones took the form of kinetosomes. But the blepharoplast 
is a definitely individualized cell organ, which the kinetosomes apparently 
are not; and although it is newlv formed at a particular stage in ontogeny, 
there can be little doubt that it is an ancient structure phylogenetically. 
Peeuliarities of Mitosis in the Bryophytes. 
The present study has shown that the general course of karyokinesis 
and cytokinesis is the same in the antheridial cells of Polytrichum as in the 
cells of pteridophytes and spermatophytes. Nevertheless, the mitoses 
herein described are distinguished by certain features some or all of which, 
though of minor importance as regards the main purposes of the mitotic 
process, may prove to be of phylogenetic significance. Such are the delay 
in the preparation of the nucleus for division until after the formation of 
a well-defined spindle rudiment; the swelling of the nucleus, especially 
in one dimension, at a certain stage in the prophases, until it occupies 
practically the same space that is later to be fillcd by the completed spindle; 
the equatorial aggregation of the chromatin (at least in the androcyte 
mother cell), following the swelling of the nucleus; and the final shrinkage 
of the nucleus, its membrane persisting until most of the nuclear sap has 
passed out into the cytoplasm. Even with respect to these peeuliarities, 
more or less exact parallels are likely to appear upon further study of the 
mitoses of various higher plants; as an illustration of this possibilitv, 
Stout (1911) has recently reported that in root-tip cells of Carex the 
chromosomes aggregate about the nucleole in the late prophases of division 
— a condition at least suggestive of the equatorial aggregation of the 
chromatin in Polytrichum. Yet the mitoses which I have studied are cer- 
tainlv distinguished in the wavs just noted from the ordinary course of 
nuclear division in the higher Orders of plants. 
Whether these peeuliarities or any of them generally characterize 
mitoses in bryophytes cannot yet be said; but some scattering observa- 
tions suggest such a possibility. Particularly is this true of the elongation 
of the nucleus shortly before the disappearance of the membrane. A 
similar elongation, at or about the same stage, has been observed in the 
antheridial cells of Ricciocarpus (Lewis, 1906), Marchantia (Ikeno, 1903; 
Miyake, 1905), Fegatella (Bolleter, 1905), Fossombronia (H. B. Hum- 
phrey, 1906), Pellia (Miyake, 1905; Wilson, 1911), Aneura and Makinoa 
(Miyake, 1905); in the vegetative cells of the gametophyte of Marchantia 
(Mottier, 1899; Van Hook, 1900); in germinating spores and other 
vegetative cells of Pellia (Farmer and Reeves, 1894; Davis, 1901; 
Archiv f. Zellforschung. VIII 12 
