New Yor AcricuLruRAL EXxpreriMEen't’ Savion. 891 
though pollen falls on the pistil fertilization does not result; 
(3) the pollen itself being so scanty as to render fertilization 
improbable if not impossible; (4) lack of viability in the pollen 
itself rendering it impotent not only on its own pistil but also 
on all others. For reasons which will be discussed in the latter 
part of this paper the writer considered that the first and second 
of these causes are not probable ones. The third seemed quite 
probable and the results secured by Beach and published in 
Bulletin No. 169 seemed to indicate that the fourth was one of 
the causes, if not the only cause, why certain varieties of grapes 
should be self-sterile; as the results there showed that the 
pollen of self-sterile grapes so far as tested was not generally 
potent on other self-sterile sorts. 
INVESTIGATION. 
AMOUNT OF POLLEN. 
This year observations were made on a great many different 
varieties of grapes as to the amount of pollen present. All of 
the estimates were of course approximate since pollen is a sub- 
stance which it would be very difficult if not impossible to meas- 
ure with any degree of exactness. These observations were 
made both with the naked eye and simple lens. There were 
ereat variations in the quantity of pollen present on the differ- 
ent blossoms, but the variations did not appear to be particu- 
larly significant. 
There were greater variations on different clusters of the 
same vine than normally appeared on different vines of different 
varietics. The last clusters of flowers to bloom, and sometimes 
the first, are usually not so well supplied with pollen as those 
which appear at the height of the blossoming season. Vines 
just coming into beariug and having only one or two clusters 
on the vine were usually scantily supplied with pollen. With 
some of the varieties, even where there was no apparent cause 
in the condition of the vine, the amount of pollen present was 
apparently insufficient to make pollination at all certain. How- 
ever, with most of the self-sterile varieties the pollen was 
quite plentiful and apparently quite sufficient for pollinating 
purposes. | 
