Notes on Pinguicula, Sect. Orcheosanthus

Abstract

The long-spurred, or orchid-flowered species of Pinguicula (Lentibulariaceae), comprise a small group of closely related taxa in Mexico and Guatemala. About eight species have been described. One of these, P. gypsicola Brandg. (Univ. Calif. Publ. Bot. 4: 190. 1911), is seemingly unique in having the summer leaves linear-lanceolate. The other so-called species, with obovate, rotund or spatulate summer leaves, are scarcely distinguishable from one another, and their taxonomic positions are in doubt. Herbarium study of these plants is difficult and frustrating because the leaves and other vegetative and reproductive structures are so fragile that dried specimens are seldom adequately pr'eserved. Usually but a single flower is found on a plant, and the extraordinarily fragile pressed flowers often lose their original color and shape to a very large extent. Often neither vegetative nor reproductive structures can be studied without severe damage to the specimen. Much more field-work is needed. Five years ago we undertook a study of variation in these long-spurred Pinguiculas as they occur in Mexico. Our conclusion, after some field-study and after examination of much herbarium material, was almost the same as that stated by Barnhart many years earlier: "The range of variation is enormous, but how much is seasonal, how much individual, and how much of taxonomic importance, is at present mere guesswork" (Mem. N.Y. Bot. Gard. 6: 47. 1916). We can, however, make a few general observations. Younger leaves and scapes are usually more densely pubescent than the older ones on the same plant; 2) leaf-size often increases markedly after anthesis; and 3) leaf-size, flower-size and scape-length vary considerably with the size and vigor of the plant as a whole. Perhaps more than in many other taxa of flowering plants, small (and therefore small-flowered) individuals look out of place in the populations to which they belong. The most vexing taxonomic problemn in Sect. Orcheosanthus has to do with the status of P. macrophylla HBK., P. moranensis HBK., and P. caudata Schlecht. Hemsley (Biol. Centr. Am. Bot. 2: 471. 1882), after observing some plants in cultivation, and the herbarium specimens then available to him, concluded that all these, and P. bakeriana Gard. Chron., P. orchidioides A.DC., P. flos-mulionis Morr. and P. ablongiloba DC., represented the same species. Indicating some doubt about the identity of the two species described by Kunth in the Nova Genera et Species, Hemsley took up the next oldest name, i.e. P. caudata Schlecht. Perhaps mostly-on Hemsley's authority, the name P. caudata has been' rather generally and indiscriminately applied to specimens in this group for the last 75 years. Sprague, writing nearly a helf-century after Hemsley (Kew Bull. 1928: 230-234. 1928), took a contrary point of view. He supposed that the individual species were probably distinct but closely and complexly interrelated, distinguishable chiefly by characters that are often or always lost in dried specimens (e.g. position of the spur in the fresh flower). Our own field-observations in Mexico lead us to believe that but one species,