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MALE sterility in potatoes, that is the absence of pollen from the anthers, has been shown by one of us (Salaman(i)) to behave as a recessive to male fertility. The present paper is an account of some farther experiments in the genetics of this character, particularly of crosses between two varieties in which the reciprocals give different results.Both quantity and quality of pollen were estimated by methods similar to those used by Salaman(i). Four empirical grades of quantity were employed, viz. "abundant," "medium," "small" and "very few grains." The quality of the pollen was determined by mounting a sample in water and examining microscopically. Under this treatment living and presumably healthy grains swell up, appear spherical and translucent, whilst the pores become prominent. Such grains are termed " good." Bad grains are generally smaller, irregular in outline, and often appear quite empty.Even the best samples of pollens which we have seen contain a considerable proportion of empty grains. The proportion of good grains was determined approximately by counting. THE RELATION BETWEEN QUALITY AND QUANTITY OF POLLEN.A close correlation was found to exist between quantity and quality of pollen as indeed was observed by East(2) and Salaman(i). In general the larger the quantity the higher the proportion of good grains. The constant presence of "abundant" pollen is a sure sign of a large proportion of good grains. Similarly the lowest grade of quantity-"very few grains"-is proof of the absence of good pollen. Of the intermediate grades "medium" quantity was generally associated with poor quality pollen. The grade which we describe as "small" rarely contained any good grains. Perhaps "medium" quantity is best counted as potentially fertile, the "small" quantity as potentially sterile.

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