Overtorir—On the Root Tips of Podophyllum Peltatum. 307 
ist in somatic or germ nuclei. Although I (’04, ’05, ’09a) found 
an apparently continuously chromatic spirem in the germ nuclei 
of Podophyllum, Campanula, Helleborus, and Richardia, I was 
unable to find one in Calycanthus and Thalictrum. I (’09a) 
have already suggested that in plants like Allium, etc., in which 
there is an apparently continuous chromatic spirem, there prob¬ 
ably exist individual segments or chromosomes very closely united 
without any very extensive linin intervals. Evidence against a 
continuous chromatic spirem at any stage is abundant, as is shown 
by that presented, especially by Lundegard (’10a, ’12c), Stout 
(’12), von Schustow (’13), and others. As stated, I do not find 
evidence of a continuous spirem in the root tips of Podophyllum 
which, contrary to the statement made in my preliminary reports 
(Overton, ’09&, ’ll), in which it was stated that, while the spirem 
is not continuously chromatic, the chromosomes appear to be con¬ 
nected by visible linin intervals into a definite spirem. That the 
serial arrangement and association of chromosomes has a signifi¬ 
cant bearing on the problems as to the general organization of 
the nucleus has been pointed out by Stout (’12) and Sharp (’13). 
In my former studies on the organization of the nuclei of cer¬ 
tain plants (Overton, ,05, ’09a), and in common with Rosenberg 
(’04) and several more recent authors, I have presented consider¬ 
able evidence to show that the chromosomes persist as individual 
structures in both somatic and germ cells of plants. In certain 
plants I have shown that in the somatic nuclei the chromosomes 
are represented by certain definite bodies, the prochromosomes, 
arranged in parallel pairs with apparent double linin intervals, 
and have also suggested that these heterogeneous spirems prob¬ 
ably remain distinct throughout the life history of the sporophyte. 
I have also pointed out that in such plants possessing a hetero¬ 
geneous spirem during the first meiotic division, each of the two 
parts composing each diakinetic chromosome represents a somatic 
chromosome. Each univalent portion of each bivalent diakinetic 
chromosome undergoes a longitudinal fission, forming apparent 
tetrads. 
That in certain plants the chromosomes in resting stages and 
in very early prophases do not form a complete reticulum, but 
can be observed as unit masses at all stages of nuclear develop¬ 
ment, is evidence supporting the doctrine of the individuality of 
the chromosomes. The presence of prochromosomes or similar 
bodies, as first reported by Rosenberg (’04) for Capsella, Zostera, 
