556 



THE AMERICAN NATURALIST 



[Vol. L 



Because of the number of flower types, and the fact 

 that most of our cultivated grapes are only one or two 

 generations from the wild, they would seem to furnish 

 ideal material for the study of sex inheritance. 



Two types of vines are found in the wild, those produc- 

 ing functionally pistillate flowers, but bearing reflexed 

 non-functional stamens, and those producing functionally 

 staminate flowers, but bearing suppressed pistils. 



We have then apparently a transitional form, in the 

 case of the grape, from a hermaphroditic condition such 

 as is found in the apple, in which the male and female 

 determiners are apparently linked, to the strictly diecious 

 forms, as ashes, willows, etc., in which the determiner for 

 maleness is completely suppressed in the sex chromosome 

 bearing the determiner for femaleness, and the female 

 determiner is completely suppressed in the chromosome 

 bearing the factor for maleness. 



On this hypothesis we would assume that in the func- 

 tionally pistillate grape flowers the suppression of male- 

 ness has begun and evinces itself in the production of 

 reflexed stamens bearing non-functional pollen, i. e., lack- 

 ing germ pores (Dorsey, 1913) and containing degenerate 

 generative and vegetative nuclei embedded in apparently 

 normal cytoplasm 2 (Gard, 1913). The period of degen- 

 eration of the nuclei is not at all definite.. Barely, the 

 microspore nucleus does not divide. In some cases de- 

 generation takes place directly following the microspore 

 division, in others one nucleus only will degenerate at this 

 time, and in still other cases the two nuclei will appear 

 normal at the time of dehiscence (Dorsey, 1913). Beach 

 (1899), Booth (1902) and Hedrick and Anthony (1915) 

 have shown from pollination and germination tests that 

 occasionally a few pollen grains borne in reflexed stamens 

 are entirely functional. There is an apparent lack of 

 suppression of maleness, occasionally, which allows the 

 development of these normal grains. 



Similarly it might be assumed that in the staminate 



