An Experimental Garden Test of Characters Used to Distinguish Helenium virginicum Blake from H. autumnale L.

ABSTRACT
In the most recent monographic study of the decurrent-leaved species of <em>Helenium</em>, Rock treated <em>H. virginicum</em> Blake, and the varieties of <em>H. autumnale</em> L., as a single species complex. Rock based this treatment on the apparent continuity of variation within the complex and his uncertainty as to the basis of this variation. To begin to determine if reported differences between <em>H. virginicum</em> and <em>H. autumnale</em> are genetic or phenecotypic, an experimental garden comparison of <em>H. virginicum</em> with <em>H. autumnale</em> var. <em>parviflorum</em> (Nutt.) Fern. was undertaken. Genetically based differences between these taxa were found in height, bolting date, blooming period, cauline leaf morphology and abundance, pappus length, and length of basal leaves during flowering. The presence or absence of basal leaves during flowering was found not to be a good distinguishing character. Field observations suggest that <em>H. virginicum</em> and <em>H. autumnale</em> var. <em>parviflorum</em> are ecologically isolated.