of a Hybrid Digitalis. 265 



the latter, and thus the plant might continue to grow and flourish 

 in one latitude, and yet be incapacitated for ripening its pollen 

 or perfecting its ovules unless it could also thrive upon removal to 

 another. There are certain plants, considered to be hybrids, which 

 undoubtedly reproduce their kind freely enough ; but some of 

 these at least, if not all of them, are mere varieties of the same 

 species. Thus Koelreuter ascertained that all the plants raised 

 between D. purpurea and D. thapsi, by fertilizing the ovules of 

 either by the pollen of the other, were constantly prolific, but 

 then he also ascertained that 1). thapsi itself when cultivated by 

 him, after five generations assumed all the characters of purpurea. 

 lie consequently rightly inferred that D. thapsi was to be con- 

 sidered no otherwise than as a Spanish variety of the more 

 common form of the species. If, again, it were possible for a 

 true hybrid to be fertilized by the pollen of either of its parents, 

 though it could produce no fertile pollen for itself, it would 

 then evidently be in much the same condition as the female 

 plant of any dioecious species, and its fertility might be secured 

 by the instrumentality of insects, &c. In the present plant I 

 repeatedly observed that the blossom always fell before the an- 

 thers on the shorter stamens had burst ; and in order that this 

 should not operate in diminishing the chance of impregnation, I 

 touched some of the stigmas with the pollen extracted from 

 these anthers, but without any success. Possibly however the 

 pollen was not sufficiently ripened. I also touched other stigmas 

 with the pollen of purpurea, and others again with that of lutea ; 

 but all these experiments failed in fertilizing any of the ovules. 

 Koelreuter was equally unsuccessful in his attempts to fertilize 

 this hybrid. I must here record what has appeared to me 

 a remarkable circumstance, brought before my notice during 



Vol. IV. Part II. L t 



