Rose Forms as determined by their Cytological Behaviour. 175 
In their somatic chromosome numbers both are in perfect agreement 
with the Afzelianae and Eucaninae, and are thus pentaploid. The meiotic 
features, particularly in R. sylvestris , are more atypical than in any form as 
yet described. The early stages up to diakinesis agree likewise with the 
pentaploids, but on the initiation of the heterotype spindle marked diver- 
gences become apparent. Owing to this increased disturbance, or rather as 
one of the causes thereof, the difference in behaviour between the bivalents 
and univalents is much less noticeable. Indeed, it often appears as if many 
of the chromosomes never reach the equator of the spindle at all, but begin 
to divide wherever they encounter a spindle fibre. The type of spindle 
shown more nearly approaches that of Rosa Sabini at the same stage, 
although, as in that rose, an excellent polar view of the metaphase is 
occasionally obtained (Text-fig. 3, k). However, the untidy appearance of 
the assembling chromosomes in R. Sabini depends almost certainly on the 
difference in size and shape of the chromosomes contributed by the parents, 
and, moreover, the usual double anaphase ensues in its entirety. On the 
other hand, there is no period of demarcation between the successive 
anaphases in the heterotype division of R. sylvestris. The chromosomes 
behave very curiously and seem to lose their shapes and are pulled out into 
strings and irregular masses. Notwithstanding this, it is in every way 
probable that all of the bivalent daughter chromosomes, accompanied by 
a few of the others, reach the poles. The laggards become surrounded by 
nuclear walls, forming karyomere-like structures, even before the disappear- 
ance of the spindle. Hence, in interkinesis, two larger nuclei, as well 
as a great number of smaller ones, are visible. 
The homotype division is so irregular that it is difficult to distinguish 
the positions of the main spindles. Almost certainly minor spindles 
interfere with the major ones. As a consequence, what ought to have been 
the tetrad contains numerous nuclei of varying size. Text-fig. 4, a, is not at 
