UREDINEAE 



33 



a new uredospore sorus. Towards the end of the season the same mycelium 



(sometimes in the same sorus) pro- 

 duces larger, dark brown, thick- 

 walled, two-celled teletttospores 



(Fig. 25, 5, on left, and 6). The 



latter may remain dormant for a long 

 time after falling off, and then ger- 

 minate to form, from each cell, a four- 

 celled basidium (Fig. 26, 8). Each 

 cell of the basidium (or pvomy- 

 celittrn) as shown in the figure, puts 

 out a very slender hypha {stevigWlCL) 

 ending in a minute spore, the spovi- 

 diwm. The sporidia are distributed 

 by the wind, and if one falls on a 

 barberry leaf it will germinate there, 

 producing a mycelium in the tissues, 

 and the cups on the lower surface, as 

 mentioned above. These cups are 

 known as aecidia (Fig. 27). Each 

 aecidium is bounded by a wall called 

 the pevidiVLWl) and arising from its 

 base are a number of closely packed and regularly arranged hyphae, each 



Fig. 28. Aecidium Euphorbiae Pers. Section 

 ofspermogonium. 200/1. (After De Bary) 



Fig. 29. Aecidium from leaf of Rafnia angulata. 200/1. w. T. s. 



