286 THE AMERICAN NATURALIST [Vol. XLVII 



The relation between parthenocarpy and partheno- 

 genesis of higher plants is very close, as all the known 

 cases of parthenogenesis are associated with partheno- 

 carpy, for not only embryos and seeds, but fruits develop 

 at the same time without fertilization. Since both fruits 

 and seeds which appear perfectly normal will develop, 

 although they are without embryos, one can not be posi- 

 tive about parthenogenesis unless the presence of the 

 embryo is ascertained. 



In the discussion on the causes of parthenogenesis and 

 apogamy, Winkler suggests the possibility of physico- 

 chemical changes operating in a flower in consequence of 

 non-pollination, and causing the parthenogenetic de- 

 velopment of the ovules. Also, similar changes might be 

 induced by the entrance of the pollen tube, even though 

 fertilization did not take place, as when parthenocarpic 

 fruits appear. If mutations occur which can supply the 

 proper conditions for these physico-chemical changes, 

 then it is possible to explain the inheritance of the par- 

 thenogenetic character after it has once appeared. 

 Physical changes in the cytoplasm surrounding the egg, 

 as well as changes in the osmotic pressure, are considered 

 as only theoretical explanations for parthenogenesis. If 

 they should be a cause, Winkler asks, why should these 

 changes occur in some flowers and not in others ; and if 

 they appear in ail flowers, why should not parthenoge- 

 netic embryo formations occur in all? 



One who is not acquainted with Winkler's and Blar- 

 inghem's papers should refer to the originals, as it 

 is impossible to give all the subject matter proper treat- 

 ment in a brief review. The complete bibliographies 

 appended to these papers are also well worthy of refer- 

 ence. 



Tests foe the Presence of Natural Parthenogenesis 

 in the Genus Nicotiana 

 The writer obtained no viable seed in his numerous 

 castration experiments with the exception of one doubt- 



