FEB 1964 MEMOIRS OF THE NEW YORK BOTANICAL GARDEN 10(5) :305-326 



LISTS AND KEYS OF THE CEDAR RUSTS OF THE WORLD 1 



Frank D. Kern 



Emeritus Professor of Botany, The Pennsylvania State University 



These lists and keys have been prepared in connection with a monographic 

 study of the cedar rusts (genus Gymnosporangium) of the world. It is the 

 author's belief that such a presentation will be found to have value in the 

 hands of other workers. 



Gymnosporangium was described by Hedwig. f. in de Candolle (Lamarck 

 & Candolle; Flore Francais 3rd Ed. tome 2, pp. 216 and 217). One species is 

 autoecious (G. bermudianum) on Juniperus, two species have uredial stages 

 (G. nootkatense in the United States and G. gaeumanni in Switzerland). With 

 these exceptions the species are heteroecious and demicyclic. Most of the species 

 where the life cycles are known have their aecial stages (form-genus Roestelia) 

 on the members of the Rosaceae tribe Pomeae or family Malaceae (depending 

 upon the classification used). Exceptions are G. ellisii on the bayberry family, 

 G. speciosnm on the saxifrage family, and G. extern m and G. vauqueliniae on 

 the rose family. A few are known only in the telial stage and several are known 

 only in the aecial (roestelial) stage. 



The species possess such variable characters that a generic description is 

 difficult. 



The aecia are chiefly roestelioid, i.e., with elongated peridia, cylindrical or 

 cornute, dehiscent by apical or lateral rupture ; the aeciospore wall is usually 

 colored, with numerous scattered pores. The telia may be variously shaped, ap- 

 planate or pulvinate, laterally compressed or wedge-shaped, or terete, sometimes 

 irregular, and usually expand when moistened due to the gelatinization of the 

 long pedicels. In most species there can be distinguished darker, thick-walled 

 teliospores and lighter, thin-walled teliospores. 



It is believed that the lists and keys are self-explanatory. The drawings and 

 photographs are included not so much to present the characters of certain species 

 but rather to illustrate the meaning of some of the descriptive terms. It seems 

 needless to point out that this sort of effort has its limitations, however. It must 

 be acknowledged that the keys are not strictly dichotomous and that final sepa- 

 rations may be difficult or confusing. In any event a contribution is being offered 

 toward the identities, relations, and ranges of the various species. 



In the check lists citations are included for the 55 valid species in Gym- 

 nosporangium, and the 11 names of the form species known in the aecial stage 

 only. A bibliography of publications on the genus Gymnosporangium is very 

 long. These selected references are presented as an aid to those interested in the 

 taxonomy of the genus : 



i Contribution No. 288 of the Department of Botany and Plant Pathology, The Pennsyl- 

 vania State University. 



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