278 



University of California Puhlications in Botany [Vol. 5 



Table 1 



Geimination of pollen in stigmatie fluids. FiH38 ^ A". Tabaciim var. macro- 

 phyllaxN. sylvestris; 22/07 =: N. Tab. var. macrophyUa ; 69/07 = N. sylvestris. 



Xo 

 mination Remarks 



X Stigmatie fluid from unpro- 

 tected flowers 



X Stigmatie fluid from unpro- 

 tected flowers 



X Stigmatie fluid from pro- 

 tected flowers 



X Stigmatie fluid from pro- 

 tected flowers 



X Stigmatie fluid from pro- 

 tected flowers 



Stigmatie fluid from unpro- 

 tected flowers 



Stigmatie fluid from pro- 

 tected flowers 



Stigmatie fluid from pro- 

 tected flowers 



Stiamatic fluid from pro- 

 tected flowers 



Stigmatie fluid from pro- 

 tected flowers 



Stigmatie fluid from pro- 

 tected flowers 



Stigmatie fluid from pro- 

 tected flowers 



Stigmatie fluid from pro- 

 tected flowers 



Stigmatie fluid from pro- 

 tected flowers 



Exceptional growth of pollen 

 tubes 

 X Cell dried out 



Stigmatie fluid from pro- 

 tected flowers 



Stigmatie fluid from pro- 

 tected flowers 



It seems obvious from table 1 that the physiological nature of the 

 stigmatie secretion produced in the flowers of the F^ hybrid is not 

 responsible for the failure of the hybrid pollen of apparently normal 

 constitution to produce pollen-tubes. As the table shows, the pollen 

 of both parent species germinates as rapidly and in as great amount 

 in the stigmatie fluid of the hybrid as it does in its own. Further, the 

 appearance of the plants from seed of unprotected flowers makes it 

 evident that the pollen of a number of other .Y. Tahacum varieties 

 will germinate on the stigmatie surfaces of the hybrid. None of the 

 hybrid pollen-grains, however, will germinate in their own stigmatie 

 fluid or in that of either parent. 



