THE FLORA OF SITKA, ALASKA 479 



On Alnus sitchensis (Regel) Sarg. (213). 

 Uncinula solids (DC.) Wint. The Willow mildew was collected 

 at Skagway, by the writer, July 13, 1915, on Popuhis tricho- 

 carpa T. & G. (192), but has not been observed at Sitka. 



UREDINALES. 



This interesting group of obligate parasites is quite well rep- 

 resented, and most of the species are of more or less economic 

 importance. Following the general usage the Roman numerals 

 are used in the following notes to designate the three main 

 stages in the life cycle of the rust. These are as follows : I — ■ 

 Aecia; II — uredinia; III — telia. Small bodies known as pyemia 

 are generally found in association with the aecia and sometimes 

 in association with the other forms. This stage is designated 

 by 0. 



All the species here enumerated have been determined by 

 Dr. J. C. Arthur of Lafayette, Indiana, who is recognized as 

 one of the leading authorities on the group. 



melampsorace;e. 



Melampsora biglowii'Tlmm. 



II — On Salix sitchensis Sanson. (193). The writer collected 

 this at Skagway, July 13, 1915. It has not been observed 

 at Sitka and probably does not occur, as the alternate host 

 is Larix and this tree is not found in the vicinity. 

 Pucciniastrum myrtilU (Schum.) Arth. 



II, III — On Vaccinium caespitosum Michx. (69). 



II, III — On Vaccinium ovalifolium J. E. Smith. (196). 



This rust seems to be rather infrequent. 

 Pucciniastrum pustulatum (Pers.) Diet. 



II, III— On EpiloUum affine Bong. (173), (271). 



Common and quite destructive. 

 Melampsoropsis ledicola (Peck.) Arth. 



II, III — On Ledum groenlandicum Oeder. (68). 



Common, but only moderately destructive. 

 Melampsoropsis pyrolae (DC.) Arth. 



II, III — On Moneses uniflora (L.) A. Gray. (70). 



Common and sometimes locallv destructive. 



