The Uredinia of Melampsora and Coleosporium

Abstract

phylogeny of the rusts is the uredinial peridium of Melampsora. The presence of a peridium in the uredinia of certain species of this genus was pointed out as long ago as 1899 by Klebahn (1) and more recently by Kursanov (2), by Hiratsuka (3) and by the writer (4). Whether this peridium is to be regarded as homologous with the uredinial peridium of the Pucciniastreae is an interesting question upon which fairly conclusive evidence is presented below. Two species of Melampsora, namely, M. confluens (Pers.) Jackson on Salix lutea, and M. Lini (Ehrenb.) Lev. on Linum usitatissimum, have been examined. Young uredinia of the former species were carefully fixed in the field. In passing, it may be mentioned that many of the older pustules in the collections of M. confluens were parasitized by Darluca Filum. Uredinia of M. Lini were obtained from greenhouse cultures of this rust made by Dr. A. W. Henry. Two fixing fluids, medium chromacetic acid and formalin acetic alcohol, were used, and the preparations were stained with safranin and light green. The mode of development of the uredinia of these species of Melampsora is essentially the same as has been described for M. Medusae (4). Vertical hyphae arise in palisade fashion beneath the epidermis and divide each into three enlarged cells, viz., peridial, intercalary and basal cells. The latter give rise by budding to spore-initials, while the intercalary cells are soon disorganized by the expansion of the spore-initials (Fig. 1). The peridial cells are commonly evanescent also, although they may persist beneath portions of the epidermis that have not been destroyed by the opening of the pustule. 79