8 BULLETIN 195;, U. S. DEPAETMENT OF AGRICULTUEE. 



them into the laboratory, where they were allowed to wilt slightly, 

 after which it was generally found that the pollen could be j arrcd out 

 of the terminal pores into a watch glass. In varieties which developed 

 pollen sparingly, the cells of the anthers were opened and the pollen 

 grains removed. Pollen secured in this way gave very indifferent 

 results, as a rule, and the method was superseded by the one which is 

 now in use. 



The jjresent method consists in gathering the flowers from the plants 

 about as needed. Wlien considerable numbers of crosses are to be 

 made and w^hen good flowers are abundant, a number of them are 

 gathered from each male parent to be used. These flowers are kept 

 in small paper bags similar to those used for covering the emasculated 

 flowers, each bag being properly labeled with the name or field 

 number of the variety. In this way the operator may carry a 

 considerable quantity of readily available material with him. When 

 poUen of any particular variety is desired, a flower is selected from 

 the proper bag and the corolla is pushed back between the forefinger 

 and thumb and held in such a way that the stamens lie directly across 

 the thumb-nail. After removing the pistil, the anthers are tapped 

 sharply with the forceps, and the poUen is jarred out, falling upon the 

 thumb-nail (PL III, fig. 2), whence it is readily apphed to the pre- 

 viously uncovered stigmas of the emasculated flowers (PI. I, fig. 2). 

 The bag is then replaced over the pollinated flowers, again inclosing 

 as much foliage as possible. Usually the success or failure of the cross 

 can be determined about one week after the pollen is apphed. If 

 there is a seemmg affinity between the plants crossed and if an 

 abundance of good viable pollen has been used, one will frequently 

 find an almost full-grown seed ball at the end of seven days. As a 

 rule, the crosses should be examined in five to seven days from the 

 date of pollination. In most cases, at the expiration of this time, 

 either the flower will have dropped off or the ovary will have swollen 

 sufficiently to show that the cross has been successful. In such cases 

 the paper bags should be removed and all seed balls that are devel- 

 oping should be inclosed in loose cheesecloth sacks, which should be 

 securely tied to the stems of the plants. It is hardly necessary to say 

 that a record should be made of each step in the process and that each 

 cross should be properly labeled. In Plate IV a cluster of seed balls 

 is shown and also lateral, sectional, and basal views of individual 

 seed balls. 



In connection with the methods just presented for the protec- 

 tion of the flowers from insect visitors or other possible sources 

 of outside pollination, it should be stated that two leading plant 

 breeders claim that it is unnecessary to cover the potato blossom. 

 It has been suggested by one of these breeders that the flowers are 



