— 213 — 



the description of the large variety in this F 2 (Kristofferson 1914 

 p. 28 — 30) the absurdity of giving all those different forms the 

 same name becomes obvious. F 2 comprises forms from typical 

 tricolor to typical arvensis and even forms with bright yellow 

 petals. And populations like this F 2 we find in nature, as will be 

 seen from my tables. Moreover, seeds from one plant of my po- 

 pulation F gave a segregation similar to that mentioned by Kri- 

 stofferson, reproducing most of the combinations found at 

 Frederikshavn and some more. 



Raunkiær's definition of the Isoreagent 1 ) as the final 

 unity of systematism has put an end to the chaotic state, that 

 would be the result, if we persisted in applying the old Linnean 

 definition of species in this Mendelian age of ours. We accept 

 the consequences of Mendelism and therefore we cannot say any- 

 thing about the origin or the offspring of the plants, we find 

 in nature. We know, that their appearance is the outcome of inde- 

 pendent or dependent mendeling factors. If we were able to deter- 

 mine the factors of the plants we find in nature, we would con- 

 struct the systematic units out of these. We cannot go so far, 

 but must be content to work with the outcome of the reaction 

 of those factors against the conditions. In the same manner as 

 we construct the Biotypes (Johannsen) of the genes, we con- 

 struct the Isoreagents of the characters, remembering that 

 they are not more than characters. 



In that way we get a far more rational division of the criti- 

 cal groups, than by using the old vague, uncertain and above 

 all irrationally bounded sub-species, forms, sub-forms and va- 

 rieties. 



Of course the arrangement of the isoreagents in the table 

 must not be considered as a final division of the group of Viola 

 tricolor. The other varying characters must also be examined and 

 possibly taken into consideration. This paper is an attempt to 

 show, how in dealing with the single characters we get a clearer 

 conception of the nature of the variety, that distinguishes the 



x ) »Die letzte und kleinste Einheit (nicht Einer) der Natur und der Sy- 

 stematik ist also der Inbegriff aller unter denselben Verhältnissen und auf 

 denselben Stadium isoreagierenden Individuen, und eine solche Einheit 

 nenne ich einen Isoreagenten« (Raunkiær 1918). 



All those individuals that run together in their reaction against the 

 conditions belong to the same isoreagent (Authors note). 



