Abstract
WHEN recently (July) collecting Eocene fossils in the vicinity of Roan creek, Colorado, I saw for the first time the singular composite Rudbeckia montana Gray in life. It abounds in the valleys and gulches, occupying similar positions to those in which one finds R. laciniata on the eastern side of the range. The latter, so far as I could ascertain, is absent from the region of R. montana, though it occurs in the south-western part of Colorado. The striking feature of R. montana is the total absence of rays. The large conical or cylindrical discs appear very black, slightly yellow from pollen when in flower. The involucral bracts are coarse and pointed, surrounding the base of the disc and diverging at various angles. The whole effect is most peculiar and unusual. Rayless Compositae are known in various genera, and occasionally occur as mutations in normally rayed genera. The ancestor of R. montana was presumably rayed, but losing its rays through a germinal modification, how did it manage to survive and flourish to the exclusion of the rayed form?
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