24 



BOTANICAL GAZETTE [july 



so far as the points here under discussion are concerned, than the 

 paper of 1905 (31). The close similarity of the conditions in Galtonia 

 and Tradescantia during diakinesis to those in Oenothera suggests 

 that they may be found finally to conform to Oenothera in these later 

 stages. Whether or not this will be found to be the case, we must 

 conclude that in Oenothera the longitudinal fission in the spirem 

 (however it originated) closes up, and that after the second contrac- 

 tion, or during it, the thick thread segments into the sporophyte 

 number of chromosomes. Since this diverges in important respects 

 from nearly all the recent accounts of reduction in plants, the con- 

 clusion is that reduction probably takes place differently in different 

 plants. Whether or not the results are different from the standpoint 

 of a qualitative distribution will not be discussed now. The writer 

 believes the above conclusions to be necessary, despite the fact that 

 authors have reached different conclusions in regard to the same 

 plant, particularly in such cases as Lilium and Podophyllum. 



The next important point which requires discussion and which 

 was left undecided in the statement of observations, is in regard to 

 whether the double thread observed after synapsis arises from an 

 approximation of parallel filaments or through a primary split in the 

 thread. It may be well to examine the results which follow from 

 either assumption. The writer hopes later to determine more defi- 

 nitely this difficult matter. On the first assumption of a lateral 

 approximation in synapsis of two spirems representing respectively 

 the maternal and paternal chromosomes, we should expect the double 

 thread so formed to segment into the reduced number of chromosome 

 pairs, in order to conform to the current account in forms in which 

 there is a pairing of spirems, for example Allen (i), Gregoire (16) , 

 and Yamanouchi (33). Instead, however, the spirem segments 

 into the unreduced number of bodies. We may still assume that 

 each of these bodies consists of maternal and paternal longitudinal 

 halves still closely held together and resulting from a previous approxi- 

 mation. According to this view the first mitosis would separate 

 bodies which were arranged successively on the spirem, while the 

 second mitosis would separate the maternal and paternal halves of 

 these bodies. The reason for such a result would be that the maternal 

 and paternal spirems remained closely fused after pairing, so that 





