126 BOTANICAL GAZETTE [FEBRUARY 
attention to the fact that centrospheres have been described in dividing 
spore mother-cells of Pellia epiphylla, by FARMER (6, 7, 8, 10) and 
by Davis (5). The occurrence of centrospheres here has been 
questioned, however, by GREGOIRE (13). In a recent paper, FAR- 
MER (Q) reports centrospheres and occasional centrosomes in the 
spore mother-cells of Aneura pinguts. 
In order to get good results in Riccia natans it is necessary to 
fix the material when growing rapidly. About equally good results 
were secured with chromacetic acid and with Flemming’s weaker 
solution. The sections were stained with anilin safranin and gentian 
violet. It was found best to stain deeply in gentian violet and then 
to wash out carefully. In this way all details can be brought out 
clearly, although IkENo did not find it good for Marchantia. 
The development of the antheridium has been described. When 
almost mature it consists of a large central mass of cubical cells 
surrounded by a wall one cell in thickness (fig. 33). In preparations 
from plants in which some antheridia are mature, one finds several 
stages in the development. The nuclear divisions do not take place 
simultaneously throughout an antheridium but usually all the cells 
of one of the segments marked out by the first walls dividing the 
antheridium, show the nuclei in the same stage of karyokinesis. 
In the most favorable preparations, therefore, one may find several 
stages of division in the same antheridium. 
The cells of the young antheridium are almost cubical, with finely 
granular cytoplasm. The nucleus is rarely exactly spherical and 
has a rather thick membrane. The chromatin is in an irregular 
central mass, made up of a number of pieces. A nucleolus cannot 
be distinguished. The cavity surrounding the chromatin is large 
and hyaline (figs. 53, 54). In some cases a large number of small 
bodies of chromatin were found scattered irregularly in the nuclear 
cavity. The number of chromosomes is four. It seems that the 
nuclei in the young rapidly growing antheridium rarely come to a 
typical resting stage. 
The question of the presence or absence of centrosomes in the 
cells of the young antheridium was taken up carefully, because 
previous observations on the karyokinetic figures in the sporophyte 
cells and spore mother-cells have convinced me that no such body 
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