PUCCINIA. 343 



hyphae forming the bottom of the aecidium-cup. These hyphae 

 give rise to numerous short sporophores, from each of which 

 a single long chain of spores is abjointed in basipetal succession, 

 the spores being at first separated by temporary intermediate 

 cells. The sporophores round the margin of each aecidium do 

 not, however, give off spores ; they also produce chains of 

 cells basipetally, but these grow larger and, without the inter- 

 vention of intermediate cells, remain sterile and become joined 



Fig. 183. — Puccinia graminis (Aecidium berberidis) on Berberis communis. The 

 lowest leaf and two others are seen on the upper surface, and show red spots with 

 light margins, in which the pycnidia are embedded. The other le'aves show the 

 under surface with patches of aecidia. (v. Tubeuf del) 



to their neighbours to form the peridium. Diseased portions 

 of leaves become considerably thickened. The cells of the 

 single layer of palisade parenchyma are abnormally elongated, 

 and the intercellular spaces of the spongy parenchyma, instead 

 of being large, are small and filled with mycelium. The aecidio- 

 spores escape in July to germinate on Gramineae. The germ- 

 tube enters the host by the stomata only, and develops into 

 an intercellular mycelium; this in about eight days produces 

 uredospores from cushions or sori which form lines, and break 



