r4ENETIC STUDIES IN POTATOES; STERTLTTY. 



By R. N. SALAMAN, M.A., M.D.. Burh'n. Herts. 



AND 



J. W. LESLEY, M.A., Phi,vl Brcfdliii/ Innlihih\ Ctitiliridjir Universi///. 



(Witli Plato IL) 



Male sterility in potatoos, that is tlio ahsenco of pollon from the antliors, t" 

 has been shown by one of us (8arlaiiuin(i)) to behave as a recessive to 

 male fertility. The present paper is an account of some further experi- 

 ments in the genetics of this character, particularly of crosses between 

 two varieties in which the reciprocals give difTerent results. 



Both quantity and quaUty of pollen were estimated by methods 

 similar to those used by 8alaman{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 translu- 

 cent, 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 con- 

 siderable proportion of empty grains. The projiortion of good grains was 

 determined approximately by counting. 



The Relation between Qitaltty and Qitantity of Pollen. 



.4 close correlation was found to exist between qiiantity and quality 

 of pollen as indeed was observed by P]ast(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 propor- 

 tion 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. 



