480 BOTANICAL GAZETTE [DECEMBER 
present more evidences of deterioration, and a further study of the 
illustration will show also that a large and variable number of the 
microspores have failed to attain normal development. Thus it is 
apparent that the process of degeneration in hybrid forms is in no 
way related to the processes of abortion of megaspores in the mother 
cell. The evidently pure species of the subgenus Lysimachion and 
the monotypic Zauschneria present uniformly perfect development 
of all the spores in the tetrad. In anthers showing morphological 
proof of earlier contamination, however, the number of abortive 
grains is in no way related to the number of microspores in the 
mother cell, since all the 5 possibilities of degeneration obtain. 
The pollen conditions in Clarkia are not especially different from 
those already described for Epilobium. Of 16 specimens of Clarkia 
pulchella Pursh which were examined, 8 were found to contain 
nearly uniformly potent pollen cells. The remaining 8, however, 
showed distinct evidences of hybridism, as revealed by a large 
percentage of infertile pollen. Clarkia rhomboidea Dougl. showed 
the results of degenerating influences in a far less degree, and only 
1 of 10 buds investigated presented indications of sterility. Clarkia 
Xanthina Gray exhibited features similar to those already men- 
tioned in the discussion of spore conditions in C. pulchella. One- 
half of the buds studied presented defective microspores. Fig. 13 
shows the type of pollen presented by plants possessing no morpho- 
logical evidences of spore degeneration. In contrast to this uniform 
pattern, however, fig. 14 pictures the spore conditions in plants 
which have apparently been derived from hybrid ancestors. It 
will be observed that about half of the grains are empty and 
shriveled, and are strikingly unlike the fertile cells illustrated in 
the figure. As the character of pollen sterility in Clarkia differs 
in one of the essential features relative to Epilobiwm, it will not be 
discussed at length. Furthermore, since the several species occupy 
the same region, it is but natural to assume that they are more or 
less inclined to intercross freely. The offspring from these unions, 
accordingly, show a large and varying amount of defective micro- 
spores. There is, on the other hand, a perfect development of the 
pollen where such crosses have not taken place. 
