1905] MOORE—SPOROGENESIS IN PALLAVICINIA gI 
original spore, the first mitosis of the gametophyte generation takes 
place. 
I have not been able to contribute much to a knowledge of the 
behavior of the nucleolus. It stains like the chromosomes most of 
the time, and when the latter are differentiated it becomes difficult 
to identify the nucleolus with certainty. During synapsis the nucle- 
olus is a very large and conspicuous body (fig. r). It is not so large 
during the later spirem stages, but still quite prominent (figs. 2 and 
3). At the time the spirem is ready to segment, the nucleolus shows 
a slight difference in staining reaction from the chromosomes. With 
the saffranin and gentian violet combination it takes slightly more 
gentian violet, and with the iron-alum haematoxylin it stains less 
intensely than the chromosomes. At this time it shows signs of 
fragmentation (jigs. 6 and 9g). 
Various theories regarding the constitution of the nucleolus have 
been advanced: one that it is achromatic and contributes to the forma- 
tion of the spindle; another that it is chromatic and contributes to 
the formation of the chromosomes. WAGER (18) in a recent paper 
attributes to it important functions in the organization of the chromo- 
somes and in the transmission of the hereditary substance. Its 
staining reactions would seem to ally it more closely with the chro- 
matic elements of the cell. If the nucleolus plays a part in the forma- 
tion of the achromatic spindle in the first division of Pallavicinia, 
it certainly does not in the second, since there is no reconstruction of 
the nucleus and the nucleolus is not reformed. Upon the whole the 
evidence, though by no means conclusive, indicates that the nucleolus 
in Pallavicinia may be regarded as contributing to the chromatin. 
ARMER (6) states that there are four chromosomes in Pallavicinia 
decipiens. In P. Lyellii I find eight as the reduced number in the 
spore. The count is very easily made when a polar view is obtained, 
and the compact form of the chromosomes makes the task an easy 
one. The chromosomes are in most favorable position for counting 
when viewed from the poles during metaphase and early telophase, 
as the figures clearly show (figs. 8, 9, 21, 23): 
In fig. 23 it will be observed that there are nine chromosomes. 
in one group. It is possible that the sister group would show only 
seven. In the same figure, upon the conspicuous spindle which is. 
