88 
IOWA ACADEMY OF SCIENCES. 
would argue that the abortion was not due to imperfect 
fertilization. 
Jt is well known to every horticulturist that there are 
very few plums produced or matured in comparison with 
the number of flowers produced. This fact has been dis- 
cussed by many writers, under many heads, such as self- 
sterility, abortion of pistils, etc. 
Even a cursory examination of many of our native 
plums will reveal the fact that there is a large proportion 
of the pistils not functional or abortive. There is a great 
variability in the proportion of abortive pistils in differ- 
ent varieties and different seasons. For instance, the 
Wyant plum in 1908 at Ames had only 8 per cent of per- 
fect ovaries, while the Poole’s Pride the same year had 91 
per cent. In 1904 the Wyant had about 90 per cent per- 
fect or normal ovaries. Goff (14) in 1894 tabulated results 
of counting the abortive pistils in 22 varieties, and found 
them to vary from 0 per cent in the White Nicholas to 88 
per cent in the Marianna. In the Wyant it was 16 per 
cent. Again (13) he mentions that the Moreman produced 
only 29 per cent perfect pistils. As to the variability in 
successive years he finds that the per cent of perfect pistils 
in 1892, ’98 and ’94 were 88.1 per cent, 66.1 per cent and 
5.8 per cent, respectively. He concludes (11) that the ten- 
dency to produce abortive pistils is greater in the year 
following a heavy crop, and vice versa. The number of 
young plums that form after the flower varies directly as 
the perfect pistils. Professor Waugh has also investigated 
this problem with the following results: 
Prunus Americana 27.6 per cent defective. 
Prunus chicasa 15.1 per cent defective. 
Prunus hortulaca 24.6 per cent defective. 
Prunus domestica 5 6 per cent defective. 
Prunus triflora 15.9 per cent defective. 
Lord (16) found that some trees never had pistils, while 
others that normally produced perfect pistils were without 
them some seasons. One of his shy bearers, Harrison’s 
Peach, usually had 90 per cent of the pistils defective. Oth- 
ers as the Rollingstone, He Soto, etc., rarely have more than 
