X.—The Genus Primula: Section Petiolares

Abstract

The establishment of Primula petiolaris and its allies as representing a distinct section of the genus was the work of Pax in Engler's Bot. Jahrb., x, 173 (1889). His definition of the section was reasonably adequate, allowance being made for the scanty material available to him. The main information at his disposal came from Wallich's diagnosis (1) of P. petiolaris in 1824 and Hooker's treatment (2) of that species and its varieties in 1882. The chief diagnostic marks instanced by Pax were the membranous leaves with very broad midrib and with sharply and closely erose-denticulate margin, the great variability in leaf-shape and in the degree of development of the scape, the rose-coloured flowers and the globose capsule. Very apposite were his comments on the difficulty in distinguishing the component species and his conviction that the many varieties of P. petiolaris may quite well represent individual species, although the lack of careful observations on living material compelled him to leave within that aggregate even such plants as P. Tanneri. Pax's conception of the confines of his section was better exemplified by his choice of its components than by his diagnosis.