POTATO BREEDING AND SELECTION. 9 



much more likeh" to be broken off wlieii inclosed in bags.^ On this 

 subject Salaman says: 



All my work has been earned on withoxit placing the flowers in bags. The reasons 

 for not adopting special precautions were that when bagged the flower inA^ariably 

 di'ops, that bees and the like never approach a potato flower, though a small fly often 

 liA-es in the bottom of the corolla, that the flower is constructed for self-fertilization, 

 and that the quantity of pollen is so scanty as to render fertilization by the wind in 

 the highest degree improbable. 



East - makes the following statement regarding the covering of 

 the flowers and emasculation: 



We may conclude that if we cut off all the uppermost cymes from the plant stems 

 and use for pollination only emascxilated flowers of those borne next in order, the 

 relative probability of our crosses being interfered with is negligible for all practical 

 purjDoses. This removes the necessity of shutting out light and air circulation by 

 means of bags. It is also worthy of note that the chances of success are much gi'eater 

 if the calyx and corolla are not removed during emasculation, as the style is very slender 

 and is likely to be injured. 



While the above assertions concerning the structure of the flower 

 and the comparative absence of insect visitors are admittedly true, 

 it has not been found that the bagging of the flowers necessarily 

 causes a greater number of them to drop off, provided one follows the 

 instructions aheady given and incloses a portion of the stem or 

 fohage with the flowers. The beneficial effects of inclosing foUage 

 with the flowers are beheved to be twofold: (1) It serves to fill the 

 sack and thus acts as a cushion for the flowers in windy or rainy 

 weather; (2) the inclosure of so much fohage in a paper bag insures 

 a goodly percentage of moisture from leaf transpiration and this 

 indirectly prevents the drying out of the pistil and supplies favorable 

 conditions for the germination of the pollen. 



POLLEN-PRODUCING VARIETIES. 



One of the chief difficulties confronting the potato-plant breeder 

 is that a great many of our most desirable commercial varieties 

 bloom either very sparingly or not at aU and that few of those which 

 do bloom develop viable poUen. In this connection East ^ makes 

 the following statement : 



If we regard bloasoming as invariable at some period of their life under the proper 

 condition.s, we can then divide potato varieties into four classes: 



1. Varieties whose buds drop off without opening. 



2. Varieties in which a few flowers open but full immediately. 



3. Varieties whose flowers jjersist several days but rarely produce viable jiollcn. 



4. Varieties which always ])roduco viable i>ollen. 



• Salaman, It. N. The inheritance of color and other characters in tho potato. In Jour. Ocnetics, v. 1, 

 DO. I, p. 7-»fi, 29 pi., I'JIO. f.Scp p. H.) 



»East, E. M. Technique of hybridizing the potato. In Proc. Boc. Uort. Sd., 1907, p. 35-40, 1SK)H. 

 fSec p. 37.) 



792.07"— I5ull. lO.V- 15 —2 



