A New Gymnosporangial Connection

Abstract

The genus Gymnosporangium, according to Kern,l is represented in North America by some 32 species. Of these, all but one are heteroecious, the aecial stages being found on members of the Hydrangeaceae, Rosaceae, and Malaceae families, while the telial stages are restricted to the family Juniperaceae. The single autoecious species, Gymnosporangium bermudianum, bears all its spore forms on species of Juniperus. Because of this limited selection of hosts, as well as their unique morphological characters, the members of this genus have been classed among the most restricted and isolated of the rusts. Until recently, no aecial stages were known on other than pomaceous hosts and it had been assumed that they were restricted to the family Malaceae. The first exeception to this rule was established by Arthur2 in I9o8 when Gymnosporangium exterum on Juniperus virginiana was successfully cultured on Porteranthus stipulatus, thus adding the family Rosaceae to the list of aecial hosts. The further addition of the family Hydrangeaceae was made by Arthur3 in I9II when Gymnosporangium gracilens was shown to have its aecial stage on Philadelphus and related genera. These three families are evidently closely related and are all included under the order Rosales. As a result of a series of observations, followed by successful inoculation tests, the writer is now able to extend the list to include a fourth family, the Myricaceae, and to establish the identity of Aecidium myricatum Schw. and Gymnosporangium Ellisii (Berk.) Farl. This work is a part of the series of Cultures of Uredineae that have been in progress at the Purdue Experiment Station under the direction of Dr. J. C. Arthur since I899, and is published by permission in advance of the 1914 report. The establishment of the connection between Aec. myricatum