12 BOTANICAL GAZETTE [july 



ever, that the latter are merely irregularities occurring during pollen 

 degeneration in O. lata^ for it is well known that a variety of irregu- 

 larities, in addition to the ones describedj may occur in synapsis and 

 the reduction mitosis in sterile hybrids. This leaves unexplained the 

 origin of these bodies called heterochromosomes. On the other hand, 

 the evidence from staining properties and from other considerations, 

 as given in the paper referred to, is against their origin from nucleoli. 

 The same bodies have since been found in the reduction mitoses in 

 O. Lamarckiana^ where they persist, in some cases at least, through 

 both mitoses to the formation of pollen tetrads. For the present, 

 therefore, the origin and possible significance of these bodies may be 

 considered to be a matter of doubt, in regard to which no conclusions 

 can be drawn until further evidence is obtained. 



POSSIBLE EXPLANATION OF THE CHROMOSOME NUMBERS 



number of Dossible exnlanations of the orierin of the chromosome 



will 



It 



suggested 



r 



.aid, however, that all of them appear unlikely, and no 

 n can be given on the basis of our present knowledge in 

 chromosome numbers. It is to be expected that further 

 on will disclose the sources of the extra chromosomes in 

 ckiana hybrid, but for the present some possibiUties may be 



seem 



chromosomes, that the sporophyte number of chromosomes 



time 



sum 



chromo 



somes. The experimental results of Nemec'^ and others, in which 

 somatic nuclei are made to fuse and subsequently divide, showing 

 mitotic figures with chromosomes whose number is the sum of the 

 number of chromosomes in the nuclei that entered the original fusion, 

 indicate the persistency of individual chromosomes in such cases- 

 Such results increase the probability that the number of chromosomes 

 found in the somatic tissues of an individual arose with the genesis 



JsNfeMEC, B., Ueber die Bedeutung der Chromosomenzahl. Bull. Intemat. 

 Akad. Sci. Bohfime 10:1-4, 1906, 



