STERILITIES OF WILD AND CULTIVATED POTATOES. 



17 



Table 2. — Typical results for varieties of -potatoes classed as A and B with respect to 

 ability to produce fruit, crossed with varieties placed in classes 1, 2, and 3, respectively, 

 with regard to the quality of their pollen — Continued . 



The classification of the various varieties and seedUngs studied, 

 both in regard to the condition of anthers and of pollen (classes 1, 2, 3, 

 and 4) and with respect to ability to produce fruit (classes A, B, 

 C, and D) is given in Table 3. 



Under the conditions at Presque Isle, where flowers are produced 

 in abundance, most varieties, if not all of them, are able to function 

 as seed parents when properly poUinated with viable pollen. This 

 is well shown by the very unusual development of fruit in those 

 varieties and seedlings having considerable viable pollen. Of the 

 588 seedlings of the 1921 sowin^ kept in 1922 and planted in five- 

 hill units, 81 produced seed balls to open pollination. Of the 188 

 seedlings of previous years grown in 1922, 56 were producing seed 

 balls, and for one of these, No. 39477, the fruits were especially 

 abundant (PI. VIII, fig. 1). The pollen of many of these which 

 produced fruit was tested, and in every case it was found to be in 

 class 1 (PL V, fig. 2) . A few varieties seem low in ability to produce 

 fruit (class B), but according to present data none are to be placed 

 in class C as entirely unable to produce fruit. 



Evidence of a parthenocarpic development of fruits has been found 

 in 14 varieties, including Rose No. 4 and most members of the Bur- 

 bank and Rural groups. At the time of the opening of the flowers, 

 the ovaries of many pistils are decidedly enlarged and the anthers 

 and corollas before they wither are pushed forward and to one side 

 by the rapidly enlarging ovaries (PI. VII, fig. 1). Such fruits sel- 

 dom, if ever, contain seeds (PI. VII, fig. 2) . They may reach a good 

 size, but usually fall before they are fully ripe. Several of the varieties 

 exhibiting this tendency are known to be good seed producers when 



