SEASONAL DIMORPHISM, ETC. 45 
of the modified structure observable in the variety pusilla. 
In other words Arisaema triphyllum illustrates a case of sea- 
sonal dimorphism, which might eventually lead to the segrega- 
tion of a second species, similar to the species of Gentiana 
and Euphrasia, described by Wettstein’, and Alectorolophus 
by Sterneck.’ ) 
In his very instructive work, Grundziige der geographisch- 
morphologischen Methode der Pflanzensystematik (Jena 
1898), Wettstein points out the possibility of ascertaining the 
phylogenetic relations of species by a comparison of the mor- 
phological structure and the geographical distribution. As a 
point of issue this author maintains, that a species occupying 
an area, where the conditions suffer no change, may remain 
constant, except in case of eventual hybridization or individ- 
ual variation. But, if the conditions become modified in some 
part of this area, or if the species spreads beyond the limits of 
the regions with other conditions, the species will naturally 
adapt itself to the new environments, and so result in the de- 
velopment of a new species. Such new species may be readily 
connected with the parental, when the areas are not too re- 
mote from each other. Some transitional forms may be ob- 
served, which morphologically resemble both. If, however, 
species is capable of being distributed across areas of wide 
extent, the transitional forms may become obliterated and 
the actual relation between the parent species and the modi- 
fied form may be obscured. From whatever cause the species 
may have become modified it is evident that seasonal 
dimorphism is one of the fundamental results in\such modi- 
fication. 
Such is unquestionably the case in the European species of 
EKuphrasia and Alectrorolophus, which have become modified 
so as to represent distinct species, simply produced by the 
changes of conditions at harvest-time in the European 
meadows. 
The history of Gentiana is somewhat different. We are 
here dealing with species, some of which are so closely related 
‘to each other that “annual” or “biennial,” flowers “large” or 
2 Wettstein, R. v. Der Saison-Dimorphismus als Ausgangspunkt fiir die Bildung neuer 
Arten in Pflanzenreiche. (Ber. Deutsch. Bot. Ges. XIII: 303. Berlin 1895.) 
3 Sterneck, I. Beitrige zur Kenntniss der Gattung Alectorolophus (Oesterr. bot. 
Zeitschr. 1894.) 
