98 The Ohio Journal of Science [Vol. XVII, No. 3, 



unreduced chromosome content. In T. vidgare the chalazal 

 daughter cell gives rise to the embryo sac, while in certain cases 

 at least, it is the micropylar daughter cell which seems to 

 function in T. Icevigatum. That this distinction is constant is 

 scarcely to be expected. 



There is, however, an equally interesting, and apparently 

 constant difference in the form of the embryo-sac of the two 

 species, the embryo-sac of T. vidgare being fully one-half as 

 wide as long at maturity, while that of T. Icevigatum is scarcely 

 one-fourth to one-third as wide as long at the corresponding 

 stage. This difference is reflected to some extent in the form of 

 the ripened achenes. 



In both forms the egg-cell gives rise to the embryo sporo- 

 phyte without apparent external stimulus or sexual fusion. 

 Division of the egg cell very frequently begins a considerable 

 time before the opening of the flower and is accompanied by 

 rapid (often amitotic, according to Schorbatow^) division of the 

 endosperm nuclei. The fact that the embryo arises from an 

 unfertilized egg-cell of unreduced chromosome count makes it 

 seem advisable to employ the expression " amiotic partheno- 

 genesis" — to describe the phenomenon, rather than the term 

 "apogamy." This expression "amiotic parthenogenesis" is of 

 course the equivalent of Winkler's*' ambiguous "somatic 

 parthenogenesis." The word "apogamy," for the sake of clear- 

 ness — not the least object to be sought — should be restricted, it 

 would seem, to cases of embryo-origin from purely vegetative 

 tissue; just as the expression "true parthenogenesis" must be 

 limited to embryo-origin from an unfertilized egg of haploid 

 chromosome number. 



The heads of T. Icevigatum, the red-fruited species, contain a 

 high percentage — often between 15% and 20% — of empty or 

 sterile achenes, to be explained in some cases by an early 

 breaking down of archesporial and nucellar tissue, in other 

 cases by a failure of the ovulary to develop anything but purely 

 vegetative tissue. Empty or sterile fruits are of rarer 

 occurrence, so far as noted, in T. vidgare. 



Both forms, in all cases examined both in Nebraska and 

 Ohio, produce pollen in abundance, but even cursory inspection 

 shows the grains to vary extremely in size. Cytological studies 

 of both species reveal varying degrees of pollen degeneration. 



Many anthers, particularly in the case of T. vidgare, contain 

 in whole or in part pollen grains of normal appearance and even 



