THE POLLEN OF CRATAEGUS HARBISONI 
Perfect and imperfect grains seem to be present in about equal numbers. 
Although C. Har- 
bisoni has been described as a good species, the condition of the pollen reminds one of such 
cases as the Velvet Bean artificial hybrids, where exactly one-half of the pollen was worth- 
less. 
of hawthorn are not species at all, but natural hybrids. 
the overlapping in distribution areas 
of the two large groups. Massachu- 
setts, southern Vermont, Connecticut, 
Rhode Island, New York, Pennsylvania 
and Delaware are states common to 
both the Coccineae and the Intricatae, 
as are also the mountainous regions 
south through Virginia, North Carolina, 
Tennessee and northern Georgia and 
Alabama. 
It seems to me highly probable that 
the Intricatae—this group of compara- 
tively new species which are also so 
closely allied to the Coccineae that the 
older systematic botanists included them 
under this last heading—may have an 
even closer -relationship with them. 
Pollen sterility is a generally accepted 
characteristic of hybrids, and the Intri- 
catae as a whole appear to share this 
trait with them. If crosses could be 
worked out with different species of the 
Coccineae for one or both of the parents, 
There is reason to suspect that ‘‘C. Harbisoni” and many other supposed species 
(Fig. 15.) 
it would not surprise me if most of the 
Intricatae could be artificially produced. 
This, however, would be a long and 
tedious experiment owing to the years 
of maturation necessary before the 
hawthorns can bear seed. Neverthe- 
less, from whatever stock the Intricatae 
may have sprung it seems to me very 
significant and a fact worthy of further 
study that the group as a whole is 
marked by such an extreme degree of 
sterility—a degree which is unusual 
even for the genus Crataegus. 
The fact that C. venusta occurs only 
in the open oak and hickory woods on 
the dry slopes of Red Mountains near 
Birmingham, Ala., made the form of 
sufficient interest for me to look up the 
other forms of Crataegus which were 
native to the state. I found that in 
Alabama alone there were described in 
Small’s second edition of his Manual of 
the Southern States, sixty-four species 
275 
