New York AGRICULTURAL EXPERIMENT STATION. 395 
MICROSCOPIC EXAMINATION. 
Besides these there is another difference between the self- 
sterile and the self-fertile pollen which is noticed on microscopic 
examination and which seems to be constant. The self-fertile 
Zzrains seem to be surrounded by a mucilaginous substance 
which makes them stick to one another more or less so that the 
pollen whether it lies dry on the slide or is placed in liquid 
media arranges itself in a succession of clumps. This mucila- 
ginous substance does not appear to be soluble in water as the 
pollen grains retain their respective positions even after several 
days in the solutions. The self-sterile pollen, on the other hand, 
shows no such arrangement but the grains distribute them- 
selves either on the slide or in the liquid like so much dry 
powder, quite by chance. 
The next phase of the work was the microscopical examination 
of the dry pollen grains to see if there were any characteristic 
differences in the size or shape of the different classes of pollen. 
All pollen, whatever its shape may be when it comes from the 
anther, swells on contact with water and most other liquids, as- 
suming an approximately spherical shape. Consequently these 
studies had to be made with the dry pollen. The results of this 
part of the work can be better illustrated than told. On the 
preceding pages are cuts which are reproduced from photo-micro- 
eraphs of the pollen mounted in balsam. The characteristic dif- 
ferences are very apparent. The self-fertile forms are oblong, 
blunt at the ends and quite symmetrical. The self-sterile sorts, 
as may be seen, are quite different in shape, being more irregular 
and usually more pointed than those of the other class. Pollen 
‘from ali other varieties in the list previously given showed these 
same shapes according to the class to which the variety in ques- 
tion belonged, but the blooming season of the first eight varieties 
was past before I thought of illustrating this phase of the work, 
and later the balsam mounts of Roscoe and Lindmar were acci- 
dentally destroyed so that illustrations of these cannot now be 
presented. | 
Examination of pollen from varieties of grapes which had given 
conflicting results in Prof. Beach’s work to determine if they were 
self sterile showed that the self-sterile and the self-fertile forms 
may be mixed in the same variety. Eaton was the first one of 
