TOTAL LACK OF GOOD POLLEN 
Longitudinal section of pollen sack of a hawthorn numbered 317 by Professor Sargent. 
Every grain in sight is shriveled or empty; there is not one which is capable}of 
germination. 
graphically or phenologically (2). The 
sum of the evidence seems to point 
just one way—when absent the plant 
may or may not be of hybrid origin; but 
when pollen sterility is present, we have 
a clear indication of mixed ancestry. 
Thus, morphologically we have a 
simple means of determining the purity 
of a species—often otherwise a difficult 
matter in the diagnosis of constant or 
relatively constant hybrids. And these 
constant hybrids are by no means as 
infrequent as we have grown to believe. 
Burbank’s ‘“‘Phenomenal,”’ a cross be- 
tween Rubus fruticosus and Rubus 
idaeus,” 1s aS constant as the purest 
species (3). The hybrid alfalfa (Medi- 
cago media), a combination of the 
common purple alfalfa and the yellow 
Such a condition is frequently found in hybrid plants. 
(Fig. 9.) 
Medicago falcata, is one of the oldest 
known hybrid races (3). It has been 
constant from the beginning as was 
proved when the cross was repeated by 
Urban. In the genus Anemone, Janc- 
zewski obtained the same results. He 
found that some characters would split, 
but that others would remain constant; 
and that when only such were present, 
hybrid races with new combinations of 
characters resulted which were as con- 
stant as the best species of the same 
genus (3). As far as I know no mor- 
phological study has been made of the 
pollen of these crosses, but they were 
quite fertile enough to reproduce them- 
selves without any appreciable diminu- 
tion in number. If found in the wild 
state, they would have been described 
2 This is practically the same as the loganberry, a hybrid which is now being widely grown 
on the Pacific Coast, and which appeared as a natural hybrid between a blackberry and red rasp- 
berry. Evidence as to whether the loganberry breeds true from seed is conflicting; certainly it 
does not always do so. 
269 
