A BAD LOT OF POLLEN GRAINS 
The hawthorn numbered ‘417 S. L.,”’ 
was good for anything. 
as species on a par with their parents. 
Such is particularly the case of the 
cross between Anemone magellanica and 
the common Anemone sylvestris. 
As I have already mentioned, hybrids 
may have all degrees of pollen sterility 
from no appreciable amount to complete 
abortion of the grains. The hybrid 
Aegilops speltiformis is a very interesting 
constant race which is sufficiently fertile 
to propagate itself (3). It was formerly 
believed by Fabre and others to be a 
transition from some wild species of 
grass to the ordinary wheat—not a cross 
but a transition. Godron was success- 
ful in producing it artificially, however, 
and found it to remain constant. He 
discovered that although the hybrid 
between Aegilops ovata—a small weed- 
and the common wheat is of itself 
sterile and produces no good pollen, 
when this in turn was fertilized by the 
pollen of the common wheat, it gave 
rise to a secondary hybrid which is no 
other than Aegilops speltiformis. 
270 
Those shown here are all shriveled and imperfect. 
seems not to have produced a single grain of pollen that 
(Fig. 10.) 
Linaria italica—a hybrid toad-flax 
between Linaria genistifolia and Linaria 
vulgaris which has been repeated by 
De Vries in his own garden (3), is so 
sterile that it has to be cross-pollinated 
before it will give its normal yield of 
seed. 
STERILITY AMONG THE 
Among the Crataegi I found on 
microscopic examination that Crataegus 
praeclara—a species grown at the Arnold 
Arboretum, and not yet described as 
far as I know—is an example of complete 
abortion. It was found to contain no 
normal pollen grains. The anthers, 
which to all external appearance were 
robust and healthy, were found to be 
nearly devoid of contents. The anther 
sack or cavity was almost entirely filled 
up by the inner wall of cells which had 
apparently grown out into the sack 
instead of being absorbed as the pollen 
grains developed. As a matter of 
fact, the pollen grains did not develop 
HAW THORNS 
