440 Stout: The Origin of Dwarf Plants 



values of the "factors" are predetermined. It is an important 

 fact established especially by Mendelian studies that qualities of 

 organs may appear and disappear independently of the organ and 

 to certain degrees independently of each other. This suggests 

 that the older conceptions of the preformation of organs as such 

 do not hold and that a hereditary unit for an organ with all its 

 characteristics does not exist. This is very clearly seen in the 

 numerous studies of inheritance and variation of color in which 

 organs like petals, leaves, and stems of plants, eyes of insects, etc., 

 re lain quite the same except for color. Such facts emphasize on 

 the one hand the wide possibilities of latency as most excellently 

 developed by De Vries, and on the other the most evident fact 

 that qualities which appear to be localized in organs are more 

 often general qualities of the entire organism, the development of 

 which is a matter of intercellular and inter-tissue relationships. 



The arguments of De Vries consistently seek to establish the 

 doctrine of the fewness of the pangens. On this basis dwarfness 

 is assumed to be the same in all the different cases in which it ap- 

 pears throughout the plant kingdom. 



No consistent uniformity, however, exists among the dwarf 

 types derived in different species or even in the same species. Some 

 types of dwarf garden peas appear to differ from tall varieties 

 chiefly in the character of the internodes. In the "brachytic" 

 varieties of cotton (Cook, 191 5) the shortened internodes a id modi- 

 fied leaves and bracts are usual! confined to the fruiting branches. 

 Numerous types of dwarf and semi-dwarf types exist in many 

 species, a notable instance of which has been recently described by 

 Bartlett (1915), who found that two dwarf types arose in a single 

 pedigreed generation of Oenothera Reynoldsii. One of these, 

 semialta, is about half as tall as f. typica and has a very dense 

 and showy inflorescence, in which the fruits and flow^ers are very 

 little smaller than in the parent form. The leaves, however, are 

 decidedly reduced. As described by Bartlett (1915. P- i3o) the 

 sister dwarf "debilis is more variable in size than mut. semialta, 

 but averages about half as high as the latter. Its fruits and flowers 

 are somewhat reduced, but by no means proportionally to the 

 plant. The leaves, on the contrary, are much ipore reduced than 

 those of mut. semialta'". 



