2 5 BOTANICAL GAZETTE [july 



idea of the pairing of threads in synapsis in Drosera, makes it highly 

 probable, and in fact necessary, that the method of reduction in the 

 Oenothera hybrid be different. This is a strong argument not 

 only against pairing of maternal and paternal spirems in Oenothera, 

 but in favor of the probability that reduction takes place in diverse 

 ways in the two genera. A considerable amount of time has already 

 been devoted to the study of reduction in this Oenothera hybrid, and 

 an account will be published later. So far as observed it shows no 

 differences in method from the account given here for the pure races. 



The hypothesis of the pairing of parental spirems in synapsis in 

 Oenothera being thus rejected, the other alternative remains, namely, 

 that the double spirem results from a split; and this appears to satisfy 

 all the facts. The observations have already shown that the spirem 

 segments into a single chain of chromosomes. The description of 

 events in Oenothera from synapsis on thus agrees in outline with the 

 1904 account of Strasburger (30) in Galtonia, and in general also 

 with that of Farmer and Moore (9) in Lilium, Osmunda, Psilotum, 

 and Aneura, Farmer and Shove (10) in Tradescantia, and Mottier 

 (19, 20) in Lilium, Podophyllum, and Tradescantia. The belief of 

 the writer is that some of these forms will be found to correspond 

 more nearly with the account which involves a pairing of threads, and 

 some with the account involving only a split. 



Another important matter which requires mention at this time 

 is the nature of the chromosome distribution which takes place on the 

 heterotypic spindle in Oenothera. As already observed, the chromo- 

 somes even during spindle formation are frequently unpaired. This 

 appears to be due to the weakness of the mutual attraction which 

 ordinarily leads to pairing. Granting that homologous maternal and 

 paternal chromosomes unite when pairing takes place, what are the 

 possibilities regarding the unpaired chromosomes? Pairing insures 

 ordinarily that the members of the pair will proceed to opposite 

 poles of the spindle, and hence that the homologous maternal and 

 paternal elements will enter different nuclei. There is no such 

 certainty in the distribution of the unpaired chromosomes, so that it 

 might be expected that in certain cases both members of a pair would 

 enter the same daughter nucleus. It is important to note that this 

 result is entirely independent of the origin of these chromosome 



