[Frcm the Bulletin of tmh Tokrby Hoi anicai. Club, 42: 429-450, /A. 2i}-27. 23 S 1915.] 



The origin of dwarf plants as shown in a sport of Hibiscus 



oculiroseus 



A. B. Stout 



(with plates 26 AXD 2?) 



The publication in 1901-1903 of Die Mutationstheorie 

 aroused a new interest in the well-known sports or spontaneous 

 variations of earlier writers. While Darwin had recognized the 

 occurrence of such variations he did not consider that they were 

 the sole means or even the most frequent means by which species 

 originated. De Vries sought to separate mutability as a type of 

 sporadic variability from fluctuating variability, to define quite 

 different laws for the two, and to ascribe to the former the only 

 power to give rise to forms of specific rank. 



Since 1901 much further evidence has accumulated regarding 

 the appearance, the behavior, and the heredity of so-called muta- 

 tions. It is fully established that marked variations do appear 

 and that these are often hereditary. This phase of the general 

 doctrine of variation is fully established. Of the various practical 

 and theoretical considerations presented by these cases none are 

 more fundamental than those relating to the expression and the 

 heredity of "newly born" characteristics. 



The general conception of mutation and the categories of be- 

 havior that indicate the process were combined by De Vries with 

 the doctrine that plant characters are to be considered as so 

 exactly represented by definite hereditary units that they can be 

 properly called "unit characters." De Vries especially em- 



429 



