Bethel: Gymnosporangium in Colorado 



159 



service in adding to our knowledge of the Rocky Mountain 

 forms, which had hitherto been much confused and largely 

 unknown. 



Note on Aecidium gracilens Peck 



Specimens of this aecium on Philadelphus occidentalis were 

 collected by Mr. G. E. Osterhout at Glenwood Springs, Colo., 

 in August, 1906. It was at that time thought by the writer to be 

 a Roestelia and was placed in his herbarium for future study. 

 The specimen was forgotten and overlooked until recently when 

 working over the roestelial forms attention was again attracted 

 to it. An investigation of the locality where the collection was 

 made revealed the presence of Gymnosporangium speciosum 

 Peck on Juniperus utahensis in close proximity. This gave a 

 suspicion that the two might be related and that A. gracilens 

 Peck might prove to be a true Roestelia. Through the kindness 

 of Dr. J. C. Arthur, the writer was permitted to examine au- 

 thentic specimens of this form and the Glenwood specimens 

 were found to be the same. This species, while referred to 

 Aecidium by Peck, possesses many characteristics of a true 

 Roestelia, among them being the elongated, membranous per- 

 idium, peridial cells loosely joined together with characteristic 

 sculpturings on the inner and side walls, and aeciospores with 

 evident germ-pores. 



An examination was then made of the distribution of the two 

 species, and the range, central Colorado to N. Mexico and Ari- 

 zona, was found to be the same. The few collections of this 

 rare aecidium, so far as can be learned, have been taken where 

 G. speciosum abounds ; likewise Philadelphus is common in most 

 localities where it has been found. 



In the cliff-dweller country (Mesa Verde National Park) 

 in southwestern Colorado, near Mancos, the writer on collecting 

 trips in 1897 and 1900 found G. speciosum epidemic on Juniperus 

 utahensis. Philadelphus was very abundant but no search was 

 made at that time for any Roestelia on it. 



In order that the attention of collectors may be directed 

 towards securing additional collections and data, the following 



