1905] MOORE—SPOROGENESIS IN PALLAVICINIA 85 
tetrad are shown entirely separated from one another. Fig. 11 
illustrates another case where the daughter chromosomes of the tetrad 
are separated. In this figure the two groups are drawn in correct 
relative positions, the one showing an almost homogenous mass, the 
other four daughter chromosomes. The fourfold character of the 
chromatic masses is most evident immediately after the segmentation 
of the chromosomes. Very soon they become more compact, and 
while they continue to show irregularities in outline, up to the meta- 
phase of mitosis, they are not so evidently composed of four elements. 
Fig. 9 presents a stage somewhat later than jig. 8. 
I have not been able to determine the origin of the tetrads with 
any certainty. Fig. 6 would seem to indicate that the elements 
of the tetrads are formed previous to the segmentation of the spirem 
and that these in some way become properly grouped. The large 
number of chromatic elements, together with the differences in their 
size and shape in this figure, are no doubt to be correlated with the 
different degrees to which the aggregations have progressed in the 
formation of the tetrads. In fig. 7 the number of masses has been 
reduced, their size is approximately uniform, and the time has almost 
arrived for the segmentation of the chromosomes. Until the origin 
of these tetrads can be made out definitely, it would be useless to 
theorize concerning them. 
While the foregoing changes take place within the nucleus, the 
outer form of that body is altered. It becomes strongly lobed, often 
assuming a tetrahedral form, one angle projecting into each lobe of 
the spore mother cell. FARMER (7) describes a similar form in 
several of the Jungermanniales studied by him, and attributes it 
to a pull by the four centrosomes which he finds in the four lobes 
of the mother cell. In describing the process for Fossombronia he 
Says “the nuclear wall is not broken, ‘although it becomes greatly 
Pulled out beneath each centrosphere, and thus the quadripolar 
spindle is so far a nuclear distortion.” 
While the tetrahedral form is perhaps the most usual at this 
Stage, it is by no means the only one. Frequently there are more 
than four projections. Such a condition as is illustrated in fig. 12 
would require the assumption of more than four centrosomes. In 
Many cases the lobes of the nucleus are rounded and do not indicate 
