324 DISEASES OF CULTIVATED PLANTS 



Rees), forms large aecidia on the outer surface of cone bracts 

 of the spruce few in number, but not constantly two, as 

 often stated; spores oblong-polyhedric, 24-33x18-22 /*, 

 warted, areolate, orange-yellow. 



Peridermiumgiganteum (Mayr.) forms barrel-shaped swellings 

 on the trunk of Pinus densiflora and P. thunbergii in Japan. 



Peridermium thomsoni, Berk. (Aecidium thomsoni, Berk.), 

 forms large, elongated aecidia on the leaves of Picea morunda^ 

 in Sikkim. 



MELAMPSORA (CAST.) 



Spermogonia forming minute, orbicular, covered patches ; 

 aecidia (caeoma) destitute of a peridium, spores in chains ; 

 uredospores aculeolate, enclosed in a more or less developed 

 peridium ; teleutospores i-celled, wedge-shaped, compacted 

 into a crust-like cushion. 



Willow-rod canker. This disease is caused by Melamp- 

 sora alii-salicis albae (Klebahn). The fungus attacks the 

 rods in the spring, forming wounds up to an inch in length. 

 The bark turns brown and becomes raised in blisters, which 

 finally crack and expose the orange-yellow mass of uredo- 

 spores. The bark sometimes remains intact for a long time, 

 but if it is broken the orange spores are seen. The rods are 

 very brittle at the diseased points, and are useless for basket- 

 making or other purposes. Later in the season the leaves 

 also bear small powdery patches of uredospores; crust-like, 

 dark-coloured patches of teleutospores also appear on the 

 leaves. The aecidium stage forms small yellow patches on 

 the leaves of various species of wild onion and garlic, as 

 Allium ursinun^ etc. The uredospore form on the rods is 

 able to perpetuate itself from year to year without the inter- 

 vention of the other forms. 



Uredospores clavate or elongated ovate, warted, 20-40 X 

 1 2- 1 8 /A; paraphyses capitate, stalk slender. 



Aecidiospores irregularly polygonal, finely warted, I7-26X 

 15-18 p. 



Teleutospores brown, i -celled, cuboid, forming a compact 

 crust under the epidermis. 



Removing diseased rods at the earliest period of the disease 

 is the only practical method of checking the disease. 



Klebahn, Zeit.fur Pflanzenkr., n, p. 21 (1902). 



