Another Gymnosporangial Connection

Abstract

Cultural proof of heteroecism in the Uredinales was made by deBary in 1864 and the fact that species of Gymnosporangium were heteroecious was proved very soon afterwards. In the spring of 1865 Oersted demonstrated by controlled inoculations the connection between Gymnosporangium Sabinae on red cedar and Roestelia cancellata on pear. During the next two years Oersted proved the life-history of Gymnosporangium juniperinumn and of Gymnosporangium clavariaeforme. We are indebted to Oersted as well as to deBary for pioneer work with the heteroecious rusts. Since those early days cultures by different workers have demonstrated the life-histories of many other species of Gymnosporangium. The telial stages are on members of the cedar family, Juniperaceae. For many species the aecial stages were found to occur on members of the apple family, Malaceae. At one time it was thought safe to conclude that the species of Gymnosporangium inhabited only hosts belonging to the families Juniperaceae and Malaceae. No telial stages have been found outside the Juniperaceae but aecial stages of three species are now known to be on hosts belonging to the Rosaceae, Hydrangiaceae, and Myricaceae, respectively. There are a few species on the members of the apple family having cupulate aecia and aeciospores with pale yellow walls. The majority of these species, however, have aecia with a cylindric or cornute peridium, peridial cells with walls variously sculptured, and aeciospores with deeply colored walls. In general these are the characteristics of the form-genus Roestelia. Two species of Roestelia have stood apart from the majority in having smooth peridial cells. One of these was described by Schweinitz as Caeonma (Roestelia) Botryapitcs on Amnelanchier