156 DISEASES OF TREES 



Puccinia striaformis .(straminis) produces a cereal rust on rye, 

 wheat, and barley. It closely resembles the foregoing disease, 

 from which it differs, however, by the ridges being smaller 

 and less elongated, and by the very short-stalked club-shaped 

 teleutospores remaining hidden by the epidermis. The aecidium 

 form is ^Ecidium asperifolii, which develops on the leaves of 

 Anchusa officinalis, Borago, Echium, &c. 



Puccinia cofonata produces a rust on cereals, especially oats. 

 Its teleutospores are provided at the shoulder with a girdle of 

 punctiform thickenings of the spore membrane. The aecidium 

 form Radium Rhamni is well known by the peculiar rich golden 

 yellow swellings which it produces on the leaves, flowers, and 

 stalks of Rhamnus cathartica and R. frangula in which it 

 develops. 



Of the large number of species of Puccinia^ the only other one 

 that need here be noticed is Puccinia Asparagi, which completes 

 its course of developmen t on the asparagus alone. The asparagus 

 rust, which may seriously devastate asparagus-beds, is best com- 

 bated by burning the halms in autumn, and by the timely 

 removal of the shoots that are first diseased. 



THRAGMIDIUM 



The species of this genus are distinguished from the species 

 of Puccinia by the teleutospores being stalked and consisting 

 of a number of cells. The groups of teleutospores which 

 develop on the under side of the leaves are preceded by uredo- 

 spores, whose orange red powder often covers the under side of the 

 leaves in large quantity. The course of development of the 

 various species has not yet been sufficiently studied.* 



Phragmidium incrassatum, the rust of the bramble, induces the 

 formation of red blotches on the leaves of Rubus fruticosus and 

 R. ccssius, and the organs consequently die prematurely. 



Phragmidium Rubi Idcei produces similar pathological sym- 

 ptoms on the leaves of Rubus Idceus. 



Phragmidium subcorticum produces the rust of the rose. 



* [All occur in this country. ED.] 



