272 Retrograde Varieties 



lings myself, many of which have already flow- 

 ered, bearing the leaves and flowers of the com- 

 mon species. Seeds of the purple reversions 

 have also been sown, and also yielded the 

 parental type only. 



Why this most curious hybrid sports so reg- 

 ularly and why others always remain true to 

 their type is as yet an open question. 



But recalling our former consideration of 

 this subject the supposition seems allowable 

 that the tendency to revert is not connected 

 with the type of the hybrid, but is apt to occur 

 in some rare individuals of every type. But 

 since most of the sterile hybrids are only known 

 to us in a single individual and its vegetative 

 offspring, this surmise offers an explanation of 

 the rare occurrence of sports. 



Finally, we must consider some of the so- 

 called hybrid races or strains of garden-plants. 

 Dahlia, Gladiolus, Amaryllis, Fuchsia, Pelar- 

 gonium and many other common flowers afford 

 the best known instances. Immeasurable 

 variability seems here to be the result of 

 crossing. But on a closer inspection the range 

 of characters is not so very much wider in these 

 hybrid races than in the groups of parent- 

 species which have contributed to the origin of 

 the hybrids. Our tuberous begonias owe their 

 variability to at least seven original parent spe- 



