POTATO BREEDING AND SELECTION. 9 
much more likely to be broken off when inclosed in bags. 1 On this 
subject Salaman says: 
All my work has been carried on without placing the flowers in bags. The reasons 
for not adopting special precautions were that when bagged the flower invariably 
drops, that bees and the like never approach a potato flower, though a small fly often 
lives 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 2 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 emasculated flowers of those borne next in order, the 
relative probability of our crosses being interfered with is negligible for all practical 
purposes. 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 greater 
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 already given and incloses a portion of the stem or 
foliage with the flowers. The beneficial effects of inclosing foliage 
with the flowers are believed 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 foliage 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 all and that few of those which 
do bloom develop viable pollen. In this connection East 2 makes 
the following statement: 
If we regard blossoming as invariable at some period of their life under the proper 
conditions, 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 fall immediately. 
3. Varieties whose flowers persist several days but rarely produce viable pollen. 
4. Varieties which always produce viable pollen. 
1 Salaman, R. N. The inheritance of color and other characters in the potato. In Jour. Genetics, v. 1, 
no. 1, p. 7-46, 29 pi., 1910. (Seep. 8.) 
2 East, E. M. Technique of hybridizing the potato. In Proc. Soc. Hort. ScL, 1907, p. 35-40, 1908. 
(See p. 37.) 
79257°— Bull. 195—15 2 
