I'arin/iiUis mid hilcrmcdiatc /''or>iis of Certain Asters. 57 



connected with the typical form, we speak of them as varie- 

 ties; we not only find this variation within the species, but the 

 outlying varieties of too closely allied species often present 

 variations approaching each other, until it is impossible to 

 draw a clear line of demarcation. 



Variation within the species, and not taking on any of the 

 characters of other species, is well represented in the set of 

 Aster cordifolius from Georgesville, near Columbus. 



Two closely allied species, approaching each other through 

 variations, is illustrated by specimens intermediate between 

 Aster Shortii and A. undulatus, between A. undulatus and A. 

 cordifolius, and between A. sagittfolius and A. Lindleyanus. 



Again, variation may be due to hybridit}-. In a certain 

 field, near Painesville, Ohio, A. undulatus and A. sagittifolius 

 grow together. I found one specimen intermediate between 

 the two species; it has the erect rigid growth of A. sagittifo- 

 lius, the close, hoary pubescence of A. undulatus, with leaf 

 characters tendingthat way, and involucre intermediate between 

 the two. Forms of A. cordifolius partaking of characters of A. 

 sagittifolius may be due to cross fertilization. A lanceolate 

 leaved form found with A. cordifolius suggests hybridization. 



In many genera the species have quite permanent charac- 

 ters, and are easy of determination. In those of wide varia- 

 tion, and when the differences blend into each other, we can 

 not always say that a certain specimen belongs to either one 

 of the two species, but must of necessit}' speak of it as inter- 

 mediate between the two. Plants presenting these variations 

 are too often disregarded by collectors. Indeed, some botan- 

 ists are inclined to look upon these intermediate forms with 

 displeasure, preserving as specimens only those that serve as 

 types to specific descriptions. It is just these intermediate 

 and puzzling forms that ought to be the most interesting, as 

 showing the gradations of connections between closely allied 

 species. Instead of bewildering the systematist, the}- aid him 

 in unraveling the snarl of intermingling characters. 



