396 PROCEEDINGS OF THE AMERICAN ACADEMY. 



XVI. 



CONTRIBUTIONS FROM THE CRYPTOGAMIC LABORATORY 

 OF HARVARD UNIVERSITY. 



XXIV. — VARIABILITY IN THE SPORES OF UREDO 

 POLYPODII (PERS.) DC. 



By B. M. Duggar. 



Presented by W. G. Farlow, October 10, 1894. 



Different opinions have been held as to the specific importance 

 of certain forms of Uredo occurring on various genera of ferns. Like- 

 wise an uncertainty has existed relative to the tvFofold nature of the 

 spores found in a single pustule. With a considerable amount of 

 material representing several host-genera, to vphich I have had access 

 through the kindness of Dr. Farlow, it has seemed of interest to give 

 the subject careful study, hoping thereby to reconcile some of the 

 views expressed. 



Winter* has referred to Uredo Polypodii (Pers.) DC. all of the 

 Uredo forms reported on many genera of ferns, the spores of this spe- 

 cies measuring 19-52 X 12-22 jx. He distinguishes, however, a forma 

 Phegopteris, on Phegopteris, based on the more or less polygonal 

 character of the rather larger spores. Schroeter t includes under 

 the same species the forms on Cystopteris fragilis and Phegopteris 

 Dryopteris, recognizing, it seems, no essential differences for the forms 

 on the two hosts. He describes the species in language resembling 

 that of Winter, but with the exception that he mentions two kinds of 

 uredospores respectively distinguished by thin and thick walls. It 

 is suggested that perhaps the thick-walled spores are teleutospores. 

 Dietel,$ after examining some American and European collections, 

 principally herbarium material, concludes that the differences in size of 

 spores and the position of the sorus on the frond between the form on 

 Phegopteris Dryopteris and the form on Cystopteris fragilis and other 



* Rabenhorst, Kryptogamenflora, Pilze I. Abth. I. p. 253. 

 t Kryptogamenflora von Sclilesien. 



J Ueber Uredo Polypodii (Pers.), Oesterreichische Botanische Zeitschrift, 

 XLIV., No. 2, February, 1894. 



