410 MEMOIRS OF THE NEW YORK BOTANICAL GARDEN 



plants may behave differently with a third self-sterile plant, one 

 combination being fertile and the other sterile. The grouping of 

 such interreactions was a point emphasized by Correns. The 

 wide fluctuations in his results, however, fully indicate that the 

 immediate cause, of self-incompatibility are strongly indi\idual 

 and are operating in different degrees of intensity in different 

 plants. The group reactions, however, may be taken to indicate 

 a degree of similarity with respect to the actual processes operating 

 among certain plants. The results in chicory show that pollen of 

 plants that are self-fertile may not be effective on other plants, 

 and that reciprocal crosses may give different results, which is 

 further evidence of the wide fluctuations in the interrelations 

 involved in fertilization. 



It is furthermore strongly indicated that the processes are 

 fluctuating in a single plant. This is seen in Jost's assumption 

 that the ([ualitative nature of the "individual stuff" is often 

 difTerent in different parts of the same plant, and in Correns' 

 suggestion that a mosaic distribution of his assumed "line stuffs" 

 might be involved in such irregular results as he obtained. In 

 chicory, feeble fertility is exhibited by the development of a low 

 percentage -of seed in comparison with the total number of flowers 

 pollinated. There is no evidence that in the ovaries setting seed 

 the processes of fertilization are identical with those in the cases 

 of most successful cross-fertilization. The need here of carefully 

 testing the relative vigor and fertility of individuals from seed 

 so produced is obvious and experiments of this sort are in progress. 

 Wliether a low or a high percentage of seed is set, the processes in 

 respect to each single fertilization involve no apparent incom- 

 patibility, or at least the incompatibility is not sufficiently strong 

 to check fertilization. It should not be assumed, however, that 

 seed-setting in and between different plants indicates an identical 

 grade of compatibility. Self- or cross-fertilization that is of a 

 weak grade of fertilization may be associated with the develop- 

 ment of such weak or poorly developed plants and strains as do 

 frequently appear in any sort of breeding. In a head of eighteen or 

 twenty flowers, all were pollinated with the same mixture of 

 pollen (in self-fertilization pollen of thest' flowers and pollen oi the 

 flowers of another head taken from the same plant and usually 

 from the same main branch), but \ar\ing numbers of seed trom 



