PROTOBASIDIOMYCETES 417 



It was very largely in characters of the uredosori and uredo- 

 spores that there was found a means of distinguishing two species, 

 or forms, as above mentioned. In the form Puccinia glumarum 

 the uredosori are described as lemon-yellow, the sori united into 

 long linear areas, while in the other form the sori are irregularly 

 distributed over the whole surface and are described as brown- 

 ocher in appearance. 



The teleutospores form sori which remain covered by the epi- 

 dermis ; the one form is said to occur more upon leaf sheaths and 

 stems, and the other upon the under surfaces of the leaves. 

 Groups of teleutospores are arranged in fan-shaped masses sur- 

 rounded by closely united, bent paraphyses. The spores are 

 broader at the apex, irregular in form, more or less angular, 

 generally 30-50^ in length, and the upper cell 14-24^ broad. 



Both of the forms here mentioned are again divisible into 

 several physiological races, each restricted to one or to relatively 

 few hosts. 



XVII. RUST OF STONE FRUITS 

 Puccinia Pruni-spinosa Pers. 



HOLWAY, E. W. D. North Amer. Uredinales 1 : 55-56. figs. 83 a, 83 b. 

 MCALPINE, D. Peach- and Plum-Leaf Rust. Victoria Dept. Agl. Guides to 



Growers 5: 1-8. 1891. 

 SCRIBNER, F. L. Leaf Rust of the Cherry, etc. U. S. Dept. Agl. Rept (1887) : 



353-355- pl-3- 



This rust occurs throughout a considerable portion of southern 

 North America. It is also found in Europe and Asia. It was in- 

 troduced into Australia, apparently, somewhat earlier than 1883, 

 and is now considerably distributed on that continent. 



This fungus has been found on various species of the genus 

 Prunus in the central and southern United States. It is reported 

 upon such hosts as the peach (Prunus Persicd) ; some of the native 

 species of plum, such as Prunus americana and Prunus domestica ; 

 and on certain cherries, especially Prunus serotina. In other sec- 

 tions of the world it has also been noted on the almond (Prunus 

 Amygdalus), on the apricot (Prunus armeniaca\ and many other 

 economic species. As a rule, this fungus is found upon the leaves, 

 but it occurs also upon fruits of peach, almond, and apricot, and 

 upon the stems of the peach under certain climatic conditions. No 



