Self-Sterility 143 



and PARK (3). This explanation seems to fit the facts 

 correctly but has certain theoretical disadvantages. 

 In any event it involves such complex Mendelian con- 

 ceptions that we shall not try to explain it here. One 

 statement, however, which was considered in the pre- 

 vious chapter again commands our attention. EAST 

 and PARK state "that modern discoveries tend more 

 and more to show that the sole function of the gameto- 

 phytes of the angiosperms is to produce sporophytes. 

 The characters which they possess appear to be wholly 

 sporophytic, the factors which they carry functioning 

 only after fertilization." This statement would seem to 

 throw out of court all consideration of the gametophyte 

 generation and would regard as impossible SELLING'S 

 theory, which is based on the direct influence of the 

 germinal equipment of gametophytes upon gameto- 

 phytes themselves. We will not enter into any general 

 discussion of this point, but merely suggest that the 

 self-sterility in the two cases might have been involved 

 with distinctly different phenomena, since SELLING'S 

 material showed degeneration and sometimes complete 

 abortion in pollen and embryo sacs, while the material 

 (Nicotiana spp.) of EAST and PARK was self-sterile 

 merely because of the failure of pollen tubes. The 

 hereditary mechanism of the two cases must be quite 

 different. 



1. BELLING, JOHN, A study of semi-sterility. Jour. Heredity 

 5:65-75. figs. 7- 1914- 



2. , A hypothesis of semi-sterility confirmed. Jour. 



Heredity 7:552. 1916. 



3. EAST, E. M., and PARK, J. B., Studies on self-sterility. I. The 

 behavior of self-sterile plants. Genetics 2:405-609. 1917. 



