634 Mutations 



The scapes are not absolutely lacking, but only 

 reduced to almost invisible rudiments. 



Relying upon this conclusion we infer that all 

 of the three elementary species have umbels, 

 some pedunculate and the others not. On this 

 point they agree with the majority of the allied 

 species in the genus and in other generas, as for 

 instance in Androsace. Hence the conclusion 

 that the common ancestors were perennial 

 plants with a rootstock bearing their flowers 

 in umbels or whorls on scapes. Lacking in the 

 Primula vera, these scapes must obviously have 

 been lost at the time of the evolution of this 

 form. 



Proceeding on this line of speculation we at 

 once see that a very adequate opportunity for 

 systematic atavism is offered here. According 

 to our general conception the apparent loss of a 

 scape is no proof of a corresponding internal 

 loss, which might as well be caused simply by 

 the reduction of the scape-growing capacity to 

 a latent or inactive state. It might be awak- 

 ■^ ened afterwards by some unknown agency, and 

 return to activity. 



Now this is exactly what happens from time 

 to time. In Holland the acaulescent primrose 

 is quite a common plant, filling the woods in the 

 spring with thousands of clusters of bright yel- 

 low flowers. It is a very uniform type, but in 



