166 BLASTOQENIC VARIATIONS. 



species; while in crosses in which a hybrid was con- 

 cerned in the parentage, out of 586, only 73.5 per cent, 

 proved fertile, showing that crosses with hybrids, 

 though fertile to a high degree, are yet rather less fer- 

 tile than crosses between species. . . A further analysis 

 of the figures shows that while hybrids crossed with the 

 pollen of pure species give 91.8 per cent, fertile, yet 

 pure species crossed with the pollen of hybrids give but 

 60 per cent, fertile." That is to say, the decline in the 

 fertility of the hybrids is due in a large measure to the 

 loss of power in the pollen of the hybrids. This decline 

 in power of the male element has been noticed before 

 in other plants by Darwin, Focke, and others. 



Rimpau * has made series of experiments on the 

 crossing of some of our common agricultural plants, and, 

 amongst other results, obtained ten artificial and nine 

 natural hybrids in wheat, and two artificial and six 

 natural hybrids in barley. His most striking result of 

 all was to obtain a fertile hybrid between wheat and 

 rye, plants belonging to different genera. Again, 

 Hurst states f that amongst Orchids no less than 150 

 bigeneric crosses are recorded. Bigeneric hybrids have 

 also been recorded J between Philesia and Lapigeria, 

 between Urceolina and Eucharis, between numerous 

 genera of Gresneracese, etc. Finally a cross has been 

 described from Digitalis ambigua (Scrophulariacese) 

 by pollen of Sinningia speciosa (Gesneracese) ; i. e., a 

 binordinal hybrid. 



* ' ' Kreutzungsproducte landwirth. Cultur-pflanzen," Berlin , 1891. 



\Loc. cit. 



i Nature, vol. Ixiv. p. 447, 1901. 



Maund's " Botanic Garden," v. p. 468. 



