Stout: The Origin of Dwarf Plants 439 



a single hereditary "pangen," but that the visible result depends 

 only partly on the direct results of the changed condition in one 

 pangen. On this point he states (1901, p. 305): "Der aussere, 

 sichtbare Erfolg hangt also nur zum Theil von der Mutation, zum 

 Theil aber auch von den alteren Merkmalen ab. Oder mit anderen 

 Worten, die neue Art kennzeichnet sich in der Regel nicht durch 

 eine enizige neue Eigenschaft, sondern dadurch, dass veile oder alle 

 Organe in bestimmter Weise umgestaltet wurden." This means 

 that in the case of Oe. nanella when the alta pangen (191 3) becomes 

 inactive it affects not only the height of the plant but also produces 

 a transformation of many other characters, such as the nature 

 of the leaves and the branching. De Vries states regarding Oe. 

 nanella (1904, p. 532): "The most remarkable feature is the 

 shape of the leaves. They are broader and shorter, and especially at 

 the base they are broadened in such a way as to become apparently 

 sessile. The stalk is very brittle, and any rough treatment may 

 cause the leaves to break off." These remarkable differences in 

 the leaves are brought about, De Vries assumes, by a change in 

 the "alta pangen", a pangen concerned with the height of the plant. 

 Such a view is, it would appear, directly opposed to a conception of 

 independence between heredity units. We get in such cases the 

 clearest possible conception of the application of De Vries's idea 

 of a heredity unit ("pangen") as an element of the germ-plasm 

 which affects and determines the character of a plant as a whole, 

 constitutionally, and in all or many of its characters. Such a 

 view is quite different from the units of Weismann, which were 

 assumed to be individual in effect and sufficiently numerous to 

 correspond directly to every detailed feature of expression. 



The original Mendelian doctrines of unit characters assumed 

 qualitative germ cell units, independent in action, and each 

 responsible for the expression of a character. Color and wrinkled- 

 ness of peas (qualities of the cotyledons) were considered as separ- 

 able hereditary units quite independent of any preformation of the 

 cotyledons themselves. Mendelian theories have been concerned 

 with the phase of development and heredity which involves 

 qualities, and though evading the difficulties of assumed spacial 

 relationship in preformation, they assume tiat the qualitative 



