1899] STUDIES ON REDUCTION IN PLANTS 19 
U radiate equally, the threads are attached at the middle; on 
those which stand so that the arms radiate unequally the threads 
are attached somewhere between the end and the middle; while 
those which stand on the end have the threads attached at the 
end of each edge. The pull of the threads attached at the dif- 
ferent points on the differently oriented pairs of chromosomes 
separate the individuals of the pair, the separation beginning at 
the point of attachment of the thread, and, as the portions are 
drawn toward the poles, the liberation proceeds until the mem- 
bers of the pair are no longer in contact. The different figures 
presented may be grouped all in three types, the V or U, the 
hook or the V with unequal arms, and the straight rods. These 
as can be readily seen are dependent on the point of attachment 
of the spindle threads. 
The result of this separation of the individuals of the paired 
chromosomes in the second mitosis is a reducing division of the 
chromosomes, or a qualitative reduction of the chromatin sub- 
stance; for, as we have seen, the paired chromosomes in the 
second mitosis are formed by the looping of longer chromo- 
somes, which often open out at the bent end before reaching the 
nuclear plate. The second division results simply in the separa- 
tion of the arms of this loop, and the distribution of each toa 
different daughter nucleus. It may be admitted here, then, with 
a feeling of reasonable confidence, that in. Trillium grandiflorum 
a reducing division of the chromosomes, or in other words, a 
qualitative reduction of the chromatin takes place during the 
second division of the nucleus in the development of the pollen 
Or microspores. One may well be cautioned against a hasty 
judgment in the interpretation of the figures presented during 
Sporogenesis, because of what seems to be contradictory evi- 
dence given by different investigators upon the question as to 
whether or not a reducing division of the chromosomes takes 
place in plants, and it is only after careful study of an excellent 
series of preparations that I am led to present this as my convic- 
tion of the nature of the process as it occurs in Trillium. The 
large size and small number of the chromosomes, as well as 
