Overton—On the Root Tips of Podophyllum Peltatum. 295 
degard (’12), Sharp (’13), and von Schustow (’13) for certain 
other plants. In Podophyllum the points of insertion of the various 
chromosomes lie in a single plane, as has been pointed out by 
von Schustow (’13) for Allium, by Sharp (’13) for Yicia, and 
by Lundegard (’12c) for other forms. Sakamura (’15) states 
that in Vida fab a the chromosomes do not lie in an equatorial 
plane. In Podophyllum the spindle fibers may be attached at 
any point to the chromosomes, this attachment resulting in var¬ 
iously formed figures as the halves of the chromosomes are pulled 
apart; this has been described by other authors and especially by 
Lundegard (’125, c), Sharp (’13) von Schustow (’13), and 
others. This condition seems to be the most common one in 
plants. 
In certain plants and animals the chromosomes have been de¬ 
scribed as segmenting transversely. In Vida fab a such pheno¬ 
mena have been mentioned by Lundegard (’125, T4), Fraser and 
Snell (’ll), and Sharp (’13), and have been fully described by 
Sakamura (’15), who holds that it is the usual occurrence in this 
plant. Such a transverse segmentation of the chromosomes of 
Podophyllum has not been observed by me. 
Lundegard (’12c) states that on account of the changes which 
the different fixing agents and stains cause it is difficult to de¬ 
termine the exact condition or constitution of the chromosomes. 
He holds that the chromosomes of Allium do not contain chromo- 
meres and describes the chromosomes in the living condition as 
being cylindrical with smooth surfaces which become roughened 
or wringled during fixation, a condition held by him to be an 
artifact. This wrinkled condition may account, according to 
Lundegard, for the conception of chromomeres, and he further 
states that on destaining the stain is retained longer in the thicker 
portions of the chromosomes. 
Strasburger and others have held that the splitting of the chro¬ 
mosomes is initiated by the splitting of discrete units or chromo¬ 
meres arranged serially along the chromosomes, which conception 
has been denied by Gregoire and his students. Bonnevie (’08) 
and Stomps (’10, ’ll) find no chromomeres in Allium and Spina- 
cia. Muller (’12) described definite chromomeres in Najas, but 
holds that the linin thread splits first, which splitting is followed 
by a splitting of the chromomeres. Sharp (’13, 205) fails to find 
evidence of chromomeres in Vida faba and Tradescantia and be¬ 
lieves that their appearance is brought about by a removal of 
