STERILITIES OF WELD AXD CULTIVATED POTATOES. 29 
able to produce fruits in abundance. There appear to be no direct 
correlations with competition for food between vegetative organs of 
storage and fruits with seeds which determine or even strongly 
influence fruit production. 
There remains, however, the question whether correlative con- 
ditions directly determine or influence either the abscission of flowers 
or the relative development of the sex organs in flowers, and par- 
ticularly of the stamens and pollen. 
The abscission of flower buds and flowers is highly variable and 
is obviously responsive to environmental influences. Special studies 
of this condition in the potato by Young (27 \ p. 17' "suggest rather 
definitely that moderately cool weather, especially at night, favors 
the setting of seed and that a gradually falling temperature with a 
moderate amount of moisture is especially favorable." Young 
notes that "it is not unusual for a wave of warm weather in early 
summer to be followed by the nearly or quite complete shedding of 
the buds and blossoms of the potato." That their environmental 
conditions operate through internal conditions and correlations is 
quite obvious. The studies which Kendall (9) has made with a 
related genus (Nicotiana) indicate that temperature is an important 
factor influencing abscission. 
When flowers of healthy potato plants remain attached until they 
are fully open and pollen is dehiscing, the general condition of stamens 
and the quantity of viable pollen appears to be very constant, at least 
for the varieties grouped in class 1. This statement is based on 
comparative studies of varieties grown at the Xew York Botanical 
Garden and at Pfesque Isle of early and late plantings of the same 
variety and of plantings grown with different fertilizers. There 
may be variations giving different grades of either maleness or 
femaleness or of both, and such variations may be rather irregular 
or decidedly cyclic. It would seem that the comparatively short 
blooming period of a potato plant limits and largely precludes the 
possibility of such noteworthy changes in sex as are seen in the 
successive flowers on a plant of Cleome spinosa (22). 
The influence of various infectious diseases on the quality of pollen 
has not been carefully studied by the writers. In the varietal test 
plats grown at Presque Isle diseased plants are rogued early, and 
material for adequate comparative tests of pollen from diseased and 
healthy plants of varieties or seedling strains normally having con- 
siderable viable pollen (in class 1) was not available. 
It is noteworthy that under conditions of abundant flowering (and 
under the same conditions) varieties like MeCormick. Green Mountain. 
Australian Blue, and Berrick exhibit characteristic differences in the 
degree of pollen sterility which are remarkably constant for each 
and which enable the general grouping into classes 1, 2, 3, and 4 to be 
made, as indicated in preceding pages. There is also evidence that 
there is no immediate and direct correlative compensation that 
causes pollen sterility. Pollen sterility is decidedly an inherent char- 
acteristic. There is obviously some hereditary basis for the con- 
dition. 
In an effort to determine the hereditary values of different grades 
of pollen sterility in potatoes Salaman (18) considers pollen fertility 
and pollen sterility rather sharply as contrasted characters and 
suggests that male sterility is here "a dominant hereditary char- 
