22 



BULUiTIX ll!»5, IT. S. DEPARTMENT OF AGRICULTURE. 



fABLE 3. — List of potato varieties studied, showing the class to which each is assignee u 

 with respect to the condition of its anthers and pollen and to its ability to produce seeo < 



I 



STERILITY IN HYBRIDS. 



The only known hybrids between species of potatoes which up to 

 the present time have been studied for imj)otonco are the (irst- 

 {2^enerati«»Ti pl.-mts of u cross between ^oUut'tin ((ndhn aiul N. chacoense 

 grown at Presque Isle in li)22. Tlicse hybrids bloomed alnmdnntly: 

 the anthers were well formed, fully colored, normally dehiscent, and 

 the pollen abundant. From one to six tests for germinatiim of pollen 

 for each of 20 plants were made, involving many thousands of {j^niins. 

 l^lump pollen grains were a cry few in number, and only live short 

 pollen tubes were seen. Tests of the pollen of the parent species at 



