-No. 642] NATURE OF BUD VARIATIONS 75 



strains of maize differing so widely in the frequency of 

 chromosome elimination or non-disjunction raises inter- 

 esting questions concerning the causes of such aberrations. 

 It would seem possible to determine by appropriate tests 

 something as to the relative influence of maternal and of 

 paternal contributions on the rate of chromosome elimi- 

 nation. 



There are circumstances connected with these results 

 from Drosophila and Zea that may raise some doubt of 

 their general applicability to cases of bud variation. The 

 Drosophila evidence is limited almost exclusively to the 

 sex chromosomes, though there is no positive evidence 

 that elimination may not occur among autosomes and re- 

 sult in non-viable individuals. The data from Zea re- 

 lates to endosperm alone, a specialized, nutritive, sterile, 

 triploid tissue. There is perhaps justification for a be- 

 lief that the sex chromosomes of animals and the triploid 

 chromosomes of the endosperm of angiosperms may be 

 subject to irregularities in behavior not commonly found 

 in other material. The only answer 'to such a contention 

 is (1) that gynandromorphs and endosperm mosaics are 

 the materials that have been critically studied and (2) 

 that there is, or should be, no presumption in favor of 

 vegetative segregation through chromosome elimination 

 or through other means as against vegetative mutation 

 or any other mechanism as a possible explanation of bud 

 variations that have not been subjected to cytological in- 

 vestigation or to critical genetic analysis. 



Cytoplasmic Segregation,— l^umerons cases of ap- 

 parent segregation of cytoplasmic elements have been 

 reported in plants. Of these, examples from Mirabilis, 

 Pelargonium, Priinula, and Zea may be noted. All of 

 them involve visible effects on chlorophyll development 

 and all show non-Mendelian inheritance. 



Correns (1909a, h) working with a white-spotted-leaved 

 type of Mirahilis observed a very irregular distribution 

 of the white and green areas, each varying from small 

 spots to whole branches. These white and green char- 

 acters were found to be inherited through the mother 

 only. The situation with respect to Pelargonium, re- 



