CHAPTEE XX 



RUST FUNGI UEEDINEAE 



None of the primary groups in the division of Fungi, as 

 adopted by Fries, were so unsatisfactory as that of the Gonio- 

 mycetes, which included with the Sphaeropsideae and the Melan- 

 conieae such heterogeneous elements as the Uredineae and the 

 Ustilagineae. More recently the two latter were combined 

 under the name of Hypodermeae, and might still be so retained 

 without grave objection, although they have little save their 

 parasitism in common. One of the most important divergences 

 is to be found in the complex character of the fructification in 

 the Uredineae, as compared with the comparative simplicity of 

 that in the Ustilagineae. The species form erumpent pustules 

 on living plants, being furnished with an innate septate 

 mycelium, but destitute of perithecia or true asci. The 

 typical fructification consists of spermogonia, aecidia, uredo- 

 spores, and teleutospores. The Spermogonia usually accompany 

 the Aecidia, and are punctiform, yellow, orange, brown, or 

 turning black ; the sporules are very small, and ovoid or 

 cylindrical, mostly expelled from a pore or orifice, at the apex 

 of the pustule, in little tendrils. The Aecidia are pale, and 

 possess a pseudoperidium, mostly in the form of a little cup, 

 when mature, with a serrate white margin, popularly termed 

 "' cluster -cups " (Fig. 115). The aecidiospores are simple, rather 

 large, usually orange and warted, produced in chains within the 

 cups, or pseudoperidia. The uredosporiferous sori are variously 

 coloured, rarely possessed of a pseudoperidium, and mostly 

 pulverulent. The uredospores are continuous, subglobose, and 

 hyaline, yellowish, or pale brown, very rarely catenulate, rather 

 large, germinating from two to six pores externally, and for 



