450 



New Phoma Disease of the Swede. 



reveals the presence of numerous septate hyphse in the cells 

 {Fig. 3) ; and the structure of the numerous small black dots 

 referred to above show them to be the pycnidia character- 

 istic of the genus Phoma. These pycnidia are special organs 

 for the production of the spores (conidia) of this fungus : each 

 pycnidium may be described as a small bag whose wall con- 

 sists of a layer of minute cells, and lining the interior are 



Fi<;. 3. — Sect::" from an attacked Swede, showing the hyphce permeating the 

 cells, and breaking down the cell walls. (Drawn with Zeiss D, oc. 4). 



special hyphae upon which the spores are born. When ripe 

 the pycnidium, which is then densely packed with spores, 

 bursts apically (Fig. 4 A, B), and the spores, adhering to 

 gether, emerge, in this species, as a small globular mass 

 of a pale or deep rose colour to carmine (Fig. 5) ; or under 

 dryer conditions they may assume a vermiculate form. 

 In a damp atmosphere the spore-mass spreads out as a 

 rose-coloured slime. The spores soon separate from each 

 other, and may then be disseminated by various agencies. 



The spores are extremely numerous and very minute, 

 measuring only 4 f.i. by 2 ju. Pure cultures were obtained 

 hy removing the spores as they emerged from the pycnidium 



