Arthur and Hotway : VIOLET RUSTS OF NORTH AMERICA. 637 



This species shows remarkable variability, especially in size 

 of the spores, and in the thickness and markings of their walls. 

 These differences come out most strikingly when comparing a 

 series of specimens. There is also considerable variability in 

 the form of the spores, as shown in Figs. 5 and 6, both taken 

 from the same specimen, but it is such as one may expect to 

 find in many other species of rusts. 



If almost any specimen of violet rust be compared critically 

 with an European specimen, the greater size of the teleutospores 

 in the former is likely to attract attention. This is the basis of 

 the species proposed by Cooke, Puccinia hastatce. A specimen 

 collected by W. C. Blasdale on Viola cognata at Sisson, Calif. 

 (Figs. 5 and 6), has been compared with the type material of 

 P. hastatce at the Kew Herbarium, through the kindness of Mr. 

 Massee, and found to agree very closely. The greater size of 

 the teleutospore in the American material generally is notice- 

 able, and this difference extends to the uredo and ascidial stages 

 as well, although not usually so pronounced. In the case of 

 an ascidium on Viola pubesccns, collected at Decorah, Iowa, in 

 1882, Farlow has made the comment: "Spores somewhat 

 larger than in the European specimens ; this may be the 

 ^Ecidium of Puccinia hastata Cke." (on the label in Ellis' N. 

 Amer. Fungi, no. 1007). If size of spores is to be taken as 

 valid basis for separating species, there is no question that the 

 American form shows a strong claim to rank as autonomous. 

 The claim, even on that assumption, is much weakened, how- 

 ever, by the great range between the smallest and largest of 

 the American specimens, indicating a decided capacity for vari- 

 ability rather than a fixed form. 



A peculiarity of the American violet rust, that in the case of 

 European specimens we have not seen mentioned and have not 

 observed, is the frequently tuberculate sculpturing of the teleu- 

 tospores. Burrill (Paras, fungi 111. : 174) makes this a diag- 

 nostic character, but in a wide series of specimens one does not 

 always meet with it. With most observers the spores would 

 generally be rated as smooth like the European form. The 

 true character of surface markings can be best studied by ob- 

 serving the spores without addition of fluids. In this way it is 

 easy to see that the markings are small papillae, sparingly dis- 

 tributed, and chiefly appearing on the upper half of the spore. 

 A closer study reveals the interesting fact that when no eleva- 



