﻿252 BOTANICAL GAZETTE [april 



Martagoiu In one respect we were correct, for in many cases 

 the V- or U-shaped chromosomes are produced by a bending, 

 either before or during the anaphase, but the fact that the V's 

 and U's are double was overlooked. 



Guignard ('99) found that in Naias major r second longitudi- 

 nal fission occurs during metakinesls of the first nuclear division 

 of the pollen mother-cell, and that each retreating daughter 

 chromosome is composed of two rod-shaped granddaughter 

 segments. 



Gregoire ('99), in the same year, observed the same to be 

 true for Lilium and Fritillaria. 



Strasburger (1900), upon reinvestigating the subject in several 

 different genera and species, found also that his explanation of 

 1895 ^^'^^ ^^^ correct one; for in all plants examined there 

 occur during the first mitosis in the pollen mother-cell two longi- 

 tudinal divisions of the chromatin, the first occurring, as the 

 writer had very clearly shown, during the early prophase, the 

 second during metakinesis, or while the daughter chromosomes 

 are on their way to the poles. The second longitudinal splitting 

 is a preparation for the second mitosis, which in Lilium does 

 not pass completely Into the structure known as the resting 

 stage. 



Since the appearance of the publications above cited, I have 

 taken up the problem again, and have followed carefully both 

 mitoses in the pollen mother-cells of Lilium Martagon, Z. candi- 

 dum, Podophyllum peltatiun, and Tradescantia virginica, together 

 with the corresponding nuclear divisions in the embryo-sac 

 mother-cell of Liliitm Martag07i, 



As regards the pollen mother-cell, I am able to confirm the 

 results of Strasburger and the two French observers, namely, 

 that during the first mitosis two longitudinal divisions of the 

 chromosomes take place. I hope, however, to present more 

 clearly certain details of the second mitosis in the pollen 

 mother-cell, together with certain facts which have hitherto 

 been too lightly touched upon, and add also the evidence which 



the embryo-sac contributes to the problem. 



eni 



described in 



