A New Genus and Other Novelties in Compositae

Abstract

a separate genus. At that time I included them in a new section, Paragynoxys. Subsequent comparisons and careful examination of abundant material of Senecio and related genera have made it evident that the group is sufficiently defined to deserve the category of a genus. This decision seems to me justified by the concurrence of the following basic characters in Paragynoxys: (1) corolla-limb divided to its base; (2) corolla white or whitish; (3) style branches with slightly enlarged and acutely or obtusely conical tips, dorsally pilose with the hairiness increasing below the apex; (4) anthers sagittate; (5) discoid cylindric head with few (generally 5) involucral bracts and few flowers; (6) unbranched or scarcely branched trees with large, coriaceous, firm, alternate, entire, more or less bunched leaves. I wish to analyze summarily each of these characters in relation with their presence in other genera or groups: Senecio, Gynoxys, Pseudogynoxys, Psacalium, Pericalia, and Odontotrichum. Vvith regard to Cacalia I think that Rydberg's conclusion' to exclude this name from the American flora is correct, and I support in this paper his interpretation substituting Psacalium, Pericalia and Odontotrichum for it. 1. Corolla. In Senecio the disc corollas are tubular and dentate, the lobes shorter than one-fourth the limb. In Gynoxys and Pericalia the division of the corolla limb is deeper, reaching one-third or one-half (exceptionally exceeding the middle of the limb as in the singularly placed G. littleii). In Psacalium and Odontotrichum the split of the limb is complete to its base. Thus the laciniate corolla distinguishes the new genus from Senecio, Gynoxys, and Pericalia but not from Psacalium and Cdontotrichum; the herbaceous habit, leaf structure and anther bases chiefly differentiate it from the last ones. See figures 1-3. 2. White corolla. W'ithout doubt, the white or pale color of the corollas is an important character, never being present in Gynoxys and extremely rare in true Senec io. 3. Style branches. Senecio and some species included by Rydberg in Odontotrichum have the typical truncate and penicillate stylar tips; only exceptional isolated species (e.g. S. aberrans Greenm.) show conical stigmas. Groups of species with lanceolate or conical stylar tips occasionally included in Senecio, having in addition another common character, e.g. vegetative, should be segregated from Senecio. The fundamental importance of the form of the stigmatic branches in the taxonomy of Compositae is generally recognized. In this connection the slightly dilated, acutely or obtusely conical style tips, not precisely penicillate, distinguish Paragynoxys well from Senecio, reinforcing the other differential characters. The style branches of Paragynoxys approach those of Gynoxys, but in this latter genus the conical or lanceolate form is more pro