The Sub-Family Arundinoideae and Its Position in Relation to a General Classification of the Gramineae

Abstract

The traditional scheme of classification for the grasses is one based upon spikelet morphology. This provides a means of identifying species and genera and of grouping them into tribes. A well-known example of a tribal scheme based entirely upon spikelet morphology is that of Hubbard in Hutchinson (1934). By the time Hubbard's work was produced the presence of parallel evolution within the family was recognized, although not always understood as no criteria were available which might reveal true affinities. Thus genera of the Pogae and Eragrostideae had for a long time been intermingled, as had genera of the Aveneae and Danthonieae. A land-mark in grass classification was established by Avdulow in 1931; he demonstrated the value of cryptic characters. Working primarily on chromosome counts he related them to tribal groups within the family, supplementing the counts with cytological and anatomical information. This approach revealed a major division between tropical and temperate grasses. Since Avdulow's pioneering work a great variety of characters has been proposed by various authors, covering the fields of anatomy, cytology, biochemistry and physiology. These have been summarized and reviewed by Prat (1960), Auquier (1963) and others. They mostly confirm Avdulow's broad groups, but many of them are indistinct or difficult to assess, and are of little help in differentiating critical groups or formulating precise circumscriptions. However among them is a group of characters derived from the leaf anatomy, which has been shown to be of considerable significance in practical taxonomy. Differences in leaf-blade anatomy were recognized by Duval-Jouve (1875) but not credited with any taxonomic significance until Avdulow re-deployed them. Since Avdulow, a mass of observations has been accumulated by various authors, of which by far the most extensive treatise is the compendium on grass anatomy of Metcalfe (1960). In this paper the terminology used is largely taken from Metcalfe's work. From the observations reported it is apparent that certain character combinations predominate, and various modern authors such as Pilger (1954), Prat (1960) and Gould (1968) have sought to employ these basic differences in leaf structure for the grouping of tribes into sub-families.