Vascular Anatomy of Monocotyledons with Secondary Growth - an Introduction

preoccupation with histological detail.It is with the object of re-instating the approaches of botanists concerned with overall aspects of growth and our own studies have been undertaken. TAXONOMIC DISTRIBUTIONThe occurrence of aborescent genera in certain families of monocotyledons which possess secondary vascular tissues is indicated in Table 1 .We treat these genera in a very broad sense but appreciate that some, notably Yucca (e.g.Trelease, 1902) have been subdivided.Two systems of classification are compared, that of various authors in Engler and Prantl (1930) and that of Hutchinson (1959) in order to emphasize that the taxonomic distribution of these plants is far from certain.We do not intend to discuss the evolutionary relationship between arborescent and herbaceous monocotyledons, but we suggest that anatomical investigation is likely to contribute significantly to a resolution of these problems.Of the listed genera, Beaucarnea, Cordyline, Dasylirion, Dracaena, and Yucca consist of species ranging in size from trees to shrubs and rhizomatous herbs.The genus Aloe is predominantly herbaceous, but includes a few aborescent Engler and Prantl 1969J