4 BULLETIN 1195, U. S. DEPARTMENT OF AGRICULTURE. 



quite as Newman and Leonian (17) have detennined 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 tlie successfid 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 sterilitj' present in 

 a variety may be made by an examination of the stamens as to the 

 size of t/he 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 OP STUDY. 



In making a special study of the anthers of varieties of the potato 



frown at Presque Isle, mature anthers ready to dehisce were fixed in 

 'lemming's fixing solution, properly embedded in parafiin, 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 inaication regarding the extent of 

 abortion of grains (PI. 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 houi-s. 

 If there was any question regarding the condition of the pollen or 

 the germination the acetocarmine stain was added. This stain shows 



