Davis. — Nuclear Studies on Pellia. 1 6 1 
in all regions of the sporophyte that have been examined. 
The chromosomes are quite small in all mitoses except those 
of the spore-mother-cell and the first two divisions in the 
spore, which are consequently most favourable for study. 
When the nucleus of the spore-mother-cell emerges from 
synapsis (Fig. 3 ) there is presented a narrow much-coiled 
spirem-thread, bearing a line of granules that seem for the 
most part to be in a single row. The spirem shortens very 
much, and at the time of segmentation presents a very 
different structure. It is much thicker, and in side view 
appears as a band whose surface bears two rows of minute 
droplets (see Figs. 7 and 8 ). However, cross-sections of the 
thread or the chromosome-segments show that the form is 
not that of a band but rather of an angled bar, and that the 
chromatin-droplets are distributed with much irregularity. 
In Fig. 17 we have presented a segment of the spirem whose 
ends are bent towards the observer, and in Fig. 18 we have 
a selected group of chromosomes as seen in cross-section. 
The angled rod-like form with the seemingly irregular dis- 
tribution of the granules is apparent from these sections and 
views. While it is quite possible that cross-sections may 
present groups of chromatin droplets in fours, as Guignard 
(’99) reports for Naias and Strasburger (’99) for a number 
of forms, the writer is convinced that no importance can be 
attached to such conditions in Pellia. There is no double 
longitudinal splitting of the mother-chromosome in Pellia , 
and the conclusions of Guignard (’99) and Strasburger (’99) 
cannot perhaps be applied as generally as we might desire. 
In this particular the present investigation conflicts with 
Farmer’s (’94) account of P allavicinia, where four chromatin 
droplets, by twice doubling, are said to give rise to sixteen 
chromosomes that then pass in groups of four to the poles 
of the quadripolar spindle. However, Farmer has shown 3 
that the mitoses in the spore-mother-cell of Hepaticae are 
usually successive, and he regards Pallavicinia as an exception 
to the general rule and an illustration of a process ‘ very 
much crowded up ’ (’94, p e 49 ). 
M 
