Notes on the Morphology of the Genus Hemileia

Abstract

This paper records the results of an examination of thirty-two species of Hemileia. Morphologically, three distinct types of sori are recognized, and it is suggested that this diversity may be used as the basis for a more accurate taxonomic treatment of the genus, although the validity of the existing species is not taken into con? sideration in this study. Hemileia vastatrix Berk and Br., the subject of a large number of papers, on account of its importance as the cause of the severe leaf disease of coffee in the Orient, is the type species of the genus Hemileia. This genus was erected in 1869 by Berkeley (2) on the basis of rust-infected coffee leaves sent to him by Thwaites from Ceylon. According to him the two main distinguishing char? acters of the genus were, (1) the stomatal sporulating habit, and (2) the characteristically reniform urediospores which were echinu? late dorsally and smooth ventrally. These two characters were supplemented by Marshall Ward's (15) discovery of single-celled, smooth and round or napiform teliospores which germinated with? out rest. The latest taxonomic treatment of the genus as a whole is that of the Sydows (11) in which twenty-three species are con? sidered, and for thirteen of these the teliospores are not recorded. Although the genus has now over forty species, in the case of over half the number the teliospores are unknown. Many species thus have been included in the genus merely on the basis of the form