Davis . — Nuclear Studies on Pellia . 159 
fine granular material that becomes distributed over a linin 
net-work. Nucleoli are also developed, and the nucleus finally 
has every appearance of being completely in a state of rest 
(see Fig. 12 ). These facts are of some importance in view 
of the opinions generallyheld that the chromosomes maintain 
their individuality in the daughter-nuclei after the first mitosis 
of the pollen- mother-cell. This conception is intimately 
concerned with, and necessarily a part of, the recent studies 
of Guignard (’99) and Strasburger (’99), on the double longi- 
tudinal splitting of the mother-chromosomes. The appearance 
of the daughter-nuclei following the first mitosis in Spermato- 
phytes is not suggestive of a resting nucleus, and yet it is 
very difficult to trace individual chromosomes in the irregular 
network of deeply staining chromatic material in the interior. 
However, some types are more favourable than others, and 
Guignard (’99) was fortunate in finding such an example in 
Naias. Strasburger has studied several forms (especially 
Trade sc antia, Larix , Allium, and P odophylluni) in which the 
chromosomes may be followed with certainty through the 
period between the first and second mitosis. The peculiar 
difficulties of investigations upon this point have been due 
in part to the interesting double longitudinal splitting, by 
which the grand-daughter-chromosomes of the second mitosis 
are prematurely organized during the first. The daughter- 
nucleus, following the first mitosis, contains the grand- 
daughter-chromosomes usually grouped with some definiteness 
in pairs, and such pairs stand for the daughter- chromosomes 
of the first mitosis. 
In Pellia we have a type where the chromosomes cannot 
be followed after the first mitosis, probably for the reason 
that they are relatively small. Whatever may be the signi- 
ficance of the deeply stained granules, one cannot discover 
any regularity in their arrangement or number. The chromo- 
somes seem to be completely lost, as is usually the case in 
successive nuclei when there is a well-defined period of rest 
between the mitoses. 
The cell-wall laid down after the first mitosis separates the 
