Polystichum Andersoni and Related Species

Abstract

Among the genera of ferns probably none has been regarded as subject to greater subspecific variation than Polystichum. How much of this supposed polymorphism is due to high variability actually existing within the species and how much to a failure to recognize constant characters peculiar to like individuals from natural geographic areas is not altogether clear. It is clear, however, that some of the widely distributed types split up into readily recognizable forms,' marked by good structural and vegetative characters, and that in many instances what might, with scant material, appear a chance variant is in reality a well characterized constant form throughout a given area, needing only to be studied in the light of ample collections to obtain recognition as a sharply defined species. The West Indian specimens, for example, had been characterized vaguely as belonging to a few variable species; yet a critical study of a large amount of material has shown' that for the most part the plants fall readily within the rather narrow limits of numerous species. These are mostly of restricted range; and although their distinguishing characters are sharply marked, it is not difficult to arrange them, on general resemblances, in natural groups whose members have obviously had