4 BULLETIN 1195, U. S. DEPARTMENT OF AGRICULTURE. 
quite as Newman and Leonian (17) have determined for certain sec- 
tions of South Carolina. Breeding the potato can scarcely be under- 
taken at the New York Botanical Garden with any hope of continued 
yearly success, and this is the situation in many other sections. The 
first condition necessary for the successful breeding of the potato is 
that of certain and profuse blooming, and it is useless to undertake 
breeding unless the environmental conditions strongly favor the 
development of flowers. 
STERILITY FROM ONE-SIDED IMPOTENCE, OR INTERSEXUALISM. 
When flowers are produced by a variety of the potato, the condi- 
tion of the sex organs as to morphological perfection and potency is 
a very important factor in seed production. Two types of sterility 
are especially concerned with the lack of potency: (1) The sterility 
of hybridity which typically affects both male and female organs alike 
and (2) the condition of intersexes which tends to give a one-sided 
sterility or abortion. In intersexes, especially from the standpoint 
of breeding, it is desirable to determine whether a plant or a clonal 
variety is able to function as a hermaphrodite, as a female, as a male, 
or perhaps as neither. 
A study of maleness and of the grades of pollen sterility present in 
a variety may be made by an examination of the stamens as to the 
size of the pollen chambers and their dehiscence, of the pollen as to 
its appearance and its viability in proper tests for germination, and 
of the ability of the pollen to function in fertilization when used to 
pollinate varieties known to be highly capable of producing fruit. 
The best experimental evidence regarding the potency of pistils, 
or the femaleness of a plant, is obtained by testing for fruit produc- 
tion by proper pollination with pollen known to be highly functional. 
Such tests, subject to experimental error, are adequate provided 
there are no marked variations in the potency of the pollen and that 
other types of sterility, particularly physiological incompatibilities, 
are not involved. 
METHODS OF STUDY. 
In making a special study of the anthers of varieties of the potato 
grown at Presque Isle, mature anthers ready to dehisce were fixed in 
Flemming's fixing solution, properly embedded in paraffin, sectioned 
by microtome, and stained with iron haematoxylin. The sections 
revealed the size and shape of the pollen chambers and the relative 
quantity of pollen, with some indication regarding the extent of 
abortion of grains (PL I, figs. 1-6). 
For more direct and exact studies the pollen of fully dehiscing 
anthers may be placed in water. Examination with a microscope 
shows that some grains swell and become plump and that others re- 
main shriveled and are obviously empty. This test was employed 
by Salaman (18) and by Salaman and Lesley (19) in judging pollen 
sterility and fertility. 
The judgment of the condition of pollen in the studies here reported 
was based on microscopical examination of pollen from healthy plants 
and pollen tubes after the grains had been on an agar-sugar culture 
medium placed in a moist chamber for a period of 18 to 24 hours. 
If there was any question regarding the condition of the pollen or 
the germination the acetocarmine stain was added. This stain shows 
