1916] FORSAITH—ON AGRACEAE 479 
rion to be impossible, its microspores are usually perfectly developed 
and there appears little indication of abortion. 
Hybrids have long been recognized in the subgenus Lysimachion, 
of which many are mentioned by HaussKNeEcut, the names and 
parentage of which can be learned by reference to his monograph 
of the genus. Since this subgenus contains so many species, 
extending over a wide and continuous territory, a study of the 
pollen conditions in connection with their geographical distri- 
bution is impossible. It is significant, nevertheless, that the 3 
species examined (Epilobium hirsutum L., E. luteum Pursh, and 
E. obcordatum Gray) showed evidences of pollen sterility. Similar 
microspore conditions were observed by JEFFREY (19) in a hybrid 
derivative of E. hirsutum. 
Since the pollen in all of these species remains in the tetrad 
formation, it furnishes an excellent example of the relation of 
abortion to the number of grains derived from the mother cell. In 
a recent discussion of this subject DeVri&s suggested that, since 
three of the megaspores in the angiosperms are sterile, we might be 
led to infer that all the higher plants are hybrids, “at least on the 
material side.” It is evident, however, that this condition has no 
bearing upon the question, since this type of degeneration repre- 
sents a constant feature, and one which is in no way affected by 
intercrossing. In contrast to this form of spore abortion, that 
mode normally exhibited by Epilobium hirsutum and E. obcordatum 
may be mentioned. In anthers which show no evidences of abor- 
tion, the 4 microspores in the tetrad develop equally, and all are 
full and fertile at maturity. Conditions analogous to these were 
found to obtain in Zauschneria. californica Presl., as indicated in 
figs.17 and 18. Those plants, nevertheless, which show indications of 
being segregates from hybrid ancestors, possessed degenerate pollen 
grains, but these defective spores bore no constant relation to the 
original number in the tetrad. Fig. 12 shows the pollen formation 
in an apparent hybrid derivative of Epilobium obcordatum Gray. 
The spores at the left of the figure are quite fully developed in 
respect to the number in the tetrad. A single exception appears 
in the lower of the two groups, where a single grain has failed to 
reach maturity. The remaining clusters, it will be observed, 
