No. 509] THE CATEGORIES OF VARIATION 259 



Retrograde varieties, according to De Vries, are 

 sharply distinguished from fhictuations t They are, as a 

 rule, constant from the start, and differ from the type 

 in only one or at most a very few respects. 



They originate for the greater part in a negative way by the ap- 

 parent loss of some quality and rarely in a positive manner by acquir- 

 ing a character seen in allied species." " By far the greatest part 

 of the ordinary garden-varieties differ from their species by a single 

 sharp character only. In derivative cases, three or even more such 

 characters may be combined in one variety, for instance, a dwarfed - 

 variety of the larkspur may at the same time bear white flowers or even 

 double white flowers, but the individuality of the single characters is 

 not in the least obscured by such combinations. 



These varieties, says De Vries, "do not possess any- 

 thing really new." The loss of a character is merely 

 apparent. "On a closer inquiry we are led to the as- 

 sumption of a latent or dormant state. The presumably 

 lost characters have not absolutely, or at least not per- 

 manently disappeared. They show their presence by 

 some slight indication of the quality they represent, or 

 by occasional reversions. They are .. ilot wanting, but 

 only latent. ' ' In other words^tj^eTonly difference be- ' 

 tween retrograde varieties an^Rhe types i the latency 

 or patency of certain charJicters. The same kinds of 

 pangens are present in the^erm plasm of both. 



Elementary species, on the other hand, 



are distinguished from their nearest allies in almost all organs. There 

 is no prominent distinctive feature between the single forms of Drab a 

 verna, Helianthemum or of Taraxacum; all characters are almost 

 equally concerned. The elementary species of Draba are characterized, 

 as we have seen, by the forms and the hairiness of the leaves, the 

 number and height of the flower stalks, the breadth and incision of the 

 petals, the forms of the fruits, and so on. Every one of the two 

 hundred forms included in this collective species has its own type, 

 which it is impossible to express by a single term. Their names are 

 chosen arbitrarily. Quite the contrary is the case with most of the 

 varieties, for which one word ordinarily suffices to express the whole 

 difference. 



The most important distinction which De Vries draws 

 between retrograde varieties and elementary species is 

 a physiological one. They 



