1897 ] LIFE HISTORY OF LILIUM PHILADELPHICUM 439 
would seem to be an inheritance from a true thallus with regular 
cell walls. 
GENERAL DISCUSSION. 
Chromosomes.—It has been claimed by botanists, especially 
Guignard and Strasburger, that during the karyokinetic division 
of the reduction nucleus in plants the chromosomes undergo 
longitudinal division just as in ordinary vegetative cells. This has 
also been maintained by Boveri, Hertwig, and Brauer in regard 
to Ascaris, where the so-called ‘‘tetrad” is said to arise by a 
double longitudinal splitting of the primary chromatin rod. 
Recently, however, it has been found by Rickert, Hacker, and 
vom Rath, that in certain arthropods each “tetrad” arises by 
one longitudinal and one transverse division of the primary 
chromosome. This would make a true reduction in Weismann’s 
sense. 
Since writing the present investigation the author has read a 
paper by Calkins* in which the formation of ‘‘tetrad” chromo- 
somes is described as occurring in the spore mother cells of two 
ferns, Preris tremula and Adiantum cuneatum. The author is quite 
certain that transverse division occurs in these chromosomes, 
although he could not tell whether the reduction took place in 
the first division or in the division following. He thinks, how- 
ever, that the first division is longitudinal and the second one 
_ transverse, so that the reduction would take place in the second 
division. This, however, is merely an inference, and he seems 
to have no direct evidence as to when the transverse division 
_ takes place, if it occurs at all. Although the work is a very 
_ commendable one the author’s substitution of zoological for 
_ botanical terms seems unwise, since it is still doubtful whether 
the zoologists have arrived at the exact truth in every case or 
‘not. The term “tetrad” in connection with the chromosomes 
ts especially objectionable in botany, since “tetrad” had a 
a definite ces many years before chromosome “‘tetrads ” were 
* Chromatin reduction and ott bamating in pteridophytes. ‘Bull. Torr. Bot. 
ales os ada me 
