CROSSINtiS IN MKLANIUM-VIOLETS 283 



Wittmock's treatise, how cxcellciil it may he and in spite of the 

 tact tliat it is hased upon cultural experiments, has only limited value. 

 It is not possihie to throw all the types of our wild Mvlaiiium violets 

 into his suh-species and forms. My line 25, for example, which is 

 found on the west shores of Skane is not identical with Witthock's 

 V. (irncnsis curtiscpdki. which is a coast-form from (îottland. My line 

 2, prohably one of the most common up-land forms in Skane, is not 

 quite the same as his V. (iri)cnsis communis, the common upland form 

 in middle Sweden. Many other examples could be mentioned. 



The correctness of the idea of V. arvensis as a distinct species 

 is more than doubtful when the variation in Fo of a cross between 

 V. tricolor and V. arvensis is considered. As above is pointed out 

 most characters investigated showed an independent variation. It is 

 true, two »essential species characters», viz. the size of the corolla 

 and the development of the labellum are (probably) due to one single 

 factor; the other characters segregate probably independently. Further, 

 most of these characters showed a continuous variation. The result 

 is that continuous series of transitions are found in such a cross. Many 

 of the Fa-plants will in some characters be »typical > V. arvensis in 

 other »typical V. tricolor^ and in other intermediate. Consequently, 

 it will not be possible to put them in any of these species. The same 

 is the case with types found in nature. Line 25, for example, has the 

 species character large flowers developed in about the same degree 

 as in »typical» V. tricolor. The flower colour is the same as in V. 

 arvensis. The pollen-magazine is about intermediate. V. tricolor am- 

 motropha has the colour characters and the size of the corolla of 

 V. tricolor; the pollen-magazine is not quite closed. Thus, it is about 

 intermediate as to these characters. The same is the case with other 

 forms distinguished by Wittrock. On account of this continuous varia- 

 tion in nature and in the Fo-generation of crosses between V. tricolor 

 and V. arvensis I consider it incorrect to divide our wild Melanium 

 violets in two species. I think the only right thing to do is to go back 

 to the Linnean idea and put all the varying types together in the one 

 single species, V. tricolor L. 



Raunkiaer (1918) has stated the »isoreagents» as the final units 

 of systematism. The isoreagents are all those individuals that show 

 the same reaction with the external conditions; they are all isophene. 

 The isoreagent is thus only a new and rather unnecessary term 

 covering the well known fact that individuals exist which are morpho- 

 logically quite identical, or isophene (Johannsen, 1913). I deem it 



Hereditas /V. 19 



