Overton—On the Root Tips of Podophyllum Peltatum. 309 
chromosome halves are quantitatively and qualitatively alike. Al¬ 
though von Schustow (’13) agrees with Lundegard as to the pres¬ 
ence of chromatic strands of double origin in somatic prophases, 
he maintains that a like duality in the heterotypic prophases offers 
no proof for the theory of a parallel conjugation during matura¬ 
tion. 
Regarding the methods of reduction of chromosomes, Lunde¬ 
gard agrees with many others that the doubleness of the spirem 
in the early heterotypic prophases, unlike that of the somatic 
prophases, is due to a lateral conjugation of chromosomes. Sykes 
( ? 08) interpreted the double structures, which she observed in 
early somatic and heterotypic prophases, as a pairing of entire 
chromosomes, and I, in common with others who have found pro¬ 
chromosomes, have furnished evidence for such a view. Even 
those adherents of the parallel conjugation theory who have not 
been able to follow the entire history of the chromosomes admit 
that the lateral conjugation of threads in the early heterotypic 
prophases represents the conjugation of entire chromosomes to 
form the bivalents which are later separated during the first mei- 
otic division. 
According to the interpretation of Digby (’19), in the hetero¬ 
typic prophase a distinct parallelism arises just as in somatic 
telophasic chromosomes and not by a conjugation of chromosomes. 
Following Farmer’s view of meiosis, she holds that bivalents are 
formed by a conjugation end to end of segments of this double 
spirem, these segments separating in the first division and the 
original split functioning in the second division, so that the 
homoeotypic division is regarded as a continuation of the last pre- 
meiotic division. 
Sharp (’20a), in a review of Miss Digby’s results on Osmunda, 
points out that her view has certain advantages. 
“It allows one interpretation to be placed upon the double spirem in 
both somatic and heterotypic prophases, irrespective of the exact time at 
which the split originates, and it also helps to explain the sudden appear¬ 
ance of the split for the second maturation mitosis in the anaphase of 
the first.” 
Sharp further says that this question must, however, be settled 
by direct evidence and that its solution obviously depends upon 
the exact manner in which the telophasic transformation of the 
chromosomes and their derivation from the reticulum in the pro- 
