CHAPTER I 



LIFE-HISTORY OF PUCCINIA CARIGIS, THE NETTLE 

 AM) SEDGE RUST 



Pnccinia Caricis has two of its stages, the spermogonial and 

 secidial, on the Nettle ( Urtica dioica and other species), and 

 two others, the uredo- and teleutospore-stages, on various species 

 of Carex, especially C. paludosa. The first appearance on the 

 nettle is in the spring, about the end of April or the beginning 

 of May, when small swollen yellowish spots can be seen on the 

 upper surface of the nettle-leaves. These spots are round and 

 convex above, sunken beneath, and about 3 — 4 mm. in diameter ; 

 soon they turn orange on the upper surface, ow T ing to the 

 development thereon of the spermogones, small flagon-shaped 

 bodies walled in by a large number of slender orange hyphge 

 and filled with many hundreds of minute spore-like cells, the 

 spermatid, which are orange in mass, though singly they appear 

 colourless (Fig. 1). 



Fig. 1. P. Caricis. Section of leaf of Nettle, showing the hypertrophy 

 produced by the mycelium of the aecidium-stage ; a spermogone, on 

 the upper side of the leaf, and two secidia, one closed, on the under 

 side. The upper face of the leaf is turned downwards. x 60. 



G. U. 



