‘MANDAN RICE‐GRASS’ AND A NOMENCLATURAL PROBLEM

Abstract

THE SITUATION arising out of the naming of the new and fertile amphidiploid 'Mandan Rice-grass,' a potential member of our flora, and recentlv deseribed by Nielsen and Rogler (1952) under the genus XStiploryzopsis, brings forward a nomenclatural problem which will increasingly engage the attention of systematists both academic and applied botany. A sampling of a wide series of families which I have recently made indicates that about half of our wild flowering plant species are polyploid derivatives. Of these a goodly portion are amphidiploids, all of which arose nature at one time or another by much the same process as observed under cultural conditions 'Mandan Rice-grass.' The reticulate nature of the evolutionary process plants is but little understood by systematists; amphidiploidization is one of the forces back of the process. Not only species, but species-series, genera, and tribes can be demonstrated to have had an origin through amphidiploidy; and we are well on our way to proof that certain families also arose through this process. Taxonomists need to understand that 'Mandan Rice-grass' did not arise through the medium of artificial manipulation; it arose naturally, although cultivation, and while the care given the original amphidiploid seed may have been a factor the survival of this line, it is to be noted that a particular plant among the sterile hybrids apparently was in the habit of occasionally producing such seed. Since this F1 hybrid is a perennial, there is every likelihood that, nature and with time, at least one such seed would have lodged a place favorable for germination and so, potentially, been the start of a completely fertile new species. For the present and so far as I am aware the new 'Mandan Rice-grass' exists only field trial plots; therefore it is still the category of a cultivated plant. It is, hcqwever, one of the members of a group of hybrids between Oryzopsis hymenoides and Stipa viridula. As nearly as I can ascertain, the first name given to any plant derived from this combination was Oryzopsis caduca Beal. Regardless of its generic placement, this validly established the specific epithet and officially launched the taxon. Somewhat later, B. L. Johnson and Rogler (1943) recognized that Oryzopsis caduca was a hybrid derived from Oryzopsis hymenoides X Stipa viridula. The rather common natural occurrence of Oryzopsis X Stipa hybrids' apparently prompted them to erect the genus XStiporyzopsis, XS. caduca automatically becoming its type species. It will be found the forthcoming edition of the