450 MEMOIRS OF THE NEW YORK BOTANICAL GARDEN 



or in other plants can be shifted by continued inbreeding or self- 

 fertiHzation remains to be seen. 



In the physiological incompatibilities that appear in the selfing 

 and crossing of such non-dimorphic species as Cichorium Intybus 

 and Cardamine pratensis, as well as in such dimorphic species as 

 Primula sinensis, we see \'ery clearly that the grade of sex differ- 

 entiation within the individual may involve a relative dissimilarity 

 sufficient to limit greatly or even prohibit successful fertilization. 

 The nature of the differentiation in the sex organs of different 

 plants can also be such that all grades of both self- and cross- 

 compatibility and incompatibility may exist, as the results in 

 Cichorium fully indicate. The phenomena, on the whole, seem 

 most consistently interpreted on the general conception that the 

 possibility of successful fertilization depends on constitutional 

 similarities rather than dissimilarities. 



BlBLIOGR.\PHY 

 Adams, J. 191 6. On the germination of the pollen grains of apple 



and other fruit trees. Bot. Gaz. 61: 131-147. 

 Andronescu, D. I. 1915. The physiology of the pollen of Zea Mays 



with special regard to vitality. Thesis, Univ. of Illinois. 

 Backhouse, W. O. 191 1. Self sterility in plums. Gard. Chron. 50: 



Bartlett, H. H. 191 3. Sex forms in Plantago lanceolata. Rhodora 15: 

 173-178. 



Baur, E. 1911. Einfiihrung in die expcrimentelle Vererbungslehre. 



Burck, W. 1908. Darwin's Kreuzungsgesetz und die Grundlagen der 

 Bliitcnbiologie. Rec. Trav. Bot. Necrl. 4: 1 7-1 18. 



Castle, W. E. 1896. The early embryology of Ciona intestinalis 

 Flemming (L.). Bull. AIus. Comp. Zool. Harvard Univ. 27: 

 201-280. 



Coit, T. E. 1915- Citrus fruits. 



Collins, G. N. 1914. A more accurate method of comparing first 

 generation maize hybrids with their parents. Jour. Agr. Re- 

 search 3: 85-91. 



Compton, R. H. 191 2. IVcliminary note on the inheritance of self- 

 sterility in Reseda odorata. Proc. Cambridge Phil. Soc. 17'. 



. 1913- Phenomena aiul problems of self-sterility. New Phyto- 



logist 12: 197-206. 



Correns, C. 1912. Selbstststcrilitiit und ln(li\ idualstoffe. Festsch. 

 Med. Xat. Gcs. z. 84. Vcrsam. Deutsch. Naturf. u. Arzte. 



