u8 VARIATION 



New type persistent. Next he undertook to determine to what 

 extent these mutant pelorics would " breed true," in order to 

 compare the proportion with the previously ascertained i per 

 cent. In this he encountered difficulty because of the high 

 degree of sterility of peloric flowers. He had in all some twenty 

 plants, and pollinated artificially more than a thousand flowers. 

 Of these he says : 



Not a single one gave a normal fruit, but some small and rudimentary 

 capsules were produced bearing a few seeds. From these I had 119 flower- 

 ing plants, out of which 1 06 were peloric and the remainder (13) one-spurred. 

 The great majority (some 90 per cent) were thus shown to be true to their 

 new type. Whether the 10 per cent reverting ones were truly atavists or 

 whether they were only vicinists caused by stray pollen grains from an- 

 other culture cannot of course be determined with sufficient certitude. 



This experiment determines not only the distinctness of the 

 new type and the suddenness of its formation, but its essential 

 purity as well ; for it bred true in 90 per cent of the cases, while 

 the probability of original mutation was slight, certainly not over 

 i per cent. 



The total lack of intermediate steps in the control experi- 

 ments is significant. Their absence in nature is not less so (for 

 if they were present as transition steps toward the formation of 

 peloric races, they would certainly be discovered, particularly 

 when we remember that the species is a perennial), and the con- 

 clusion seems inevitable that the transition is abrupt, and the 

 new type, repeatedly re-formed, is without doubt to be regarded 

 as a true mutation. 



The common snapdragon, whose flowers are exceedingly un- 

 symmetrical, also has a peloric race. " But the snapdragon is 

 self-fertile, and so is its peloric variety," observes De Vries. 

 These mutations are therefore much more easily preserved, and 

 are, as we should expect, more common than in the toadflax, 

 so common and so distinct as, without a doubt, to give rise to 

 real hybrids with the old form. 



What is true of toadflax and snapdragon is held to be true of 

 unsymmetrical flowers generally ; namely, a strong tendency to 

 give rise from time to time to peloric varieties, not by gradual 

 change of the parent stock but by sudden offset, or mutation. 



