278 Retrograde Varieties 



built up of one active and one dormant unit. 



Thirdly this deviating pair will exhibit the 

 active unit which it contains, and the hybrid 

 will show the character of the parent in which 

 it was dormant. Now the active quality was 

 that of the species, and its latent state was 

 found in the variety. Hence the inference that 

 hybrids between a species and its retrograde 

 variety will bear the aspect of the species. 

 This attribute may be fully developed, and then 

 the hybrid will not be distinguishable from the 

 pure species in its outer appearance. Or the 

 character may be incompletely evolved, owing 

 to the failure of cooperation of the dormant 

 unit. In this case the hybrid will be in some 

 sense intermediate between its parents, but 

 these instances are more rare than the alternate 

 ones, though presumably they may play an im- 

 portant part in the variability of many hybrid 

 garden-flowers. 



All of these three rules are supported by a 

 large amount of evidence. The complete fertil- 

 ity of varietal hybrids is so universally acknowl- 

 edged that it is not worth while to give special 

 instances. With many prominent systematists 

 it has become a test between species and vari- 

 ety, and from our present point of view this as- 

 sumption is correct. Only the test is of little 

 use in practice, as fertility may be diminished 



