PHOMA 407 



occasions mistaken for the perithecia of the American goose- 

 berry mildew. 



Perithecia depressed, with a slightly prominent darker 

 mouth, 125-150 /x diam. Spores elliptical, 3*5-5 X 2-2*5 //.. 



Two other species of Phoma also occur on Ribes. P. ribesia 

 (Sacc.), spores 10X3*5 /* an< ^ -^ grossulariae (Schulz. and 

 Sacc.), spores 6-9x2-2*5 /x. These are not in^any way 

 injurious. 



Dryrot of swede and mangold (Phoma napobrassicae, 

 Rostr.) sometimes causes serious injury, to the roots of 

 swedes and mangolds, causing the appearance of large, dry 

 cracks penetrating deeply into the flesh, and forming a suit- 

 able entrance into the tissues for other organisms,. 



Sporangia minute, black, appearing on the surface of the 

 wounds. Conidia hyaline, 4-6x1-2 //, emerging from the 

 sporangium in a reddish, gelatinous tendril. 



Diseased roots should not be left lying about, and it is 

 important that such should not be stored along with other 

 roots. 



Potter, Journ. Bd. Agric^ 6, No. 4. 



Rostrup, Tidsskr. for Landbkonomi, R. 5, Bd. 2, p. 330 

 (1891). 



Lobelia canker. This very destructive disease to cultivated 

 lobelias was first described by Berkeley fifty years ago, under 

 the name of Phoma devastatrix. The very minute perithecia 

 appear in myriads on the stems, giving them a cankered 

 appearance. Spores elliptical, 8-ioX 4-5. In some instances 

 the spores become i-septate, suggesting the genus Ascochyta. 



Diseased plants should at once be removed, as they never 

 bloom. 



Cabbage stem rot. A destructive disease brought about by 

 Phoma brassicae (Thiim.). The stem is the part attacked, the 

 parasite forming large, roundish patches bordered with brown 

 and becoming pale towards the centre. Very frequently 

 these patches extend into each other forming large, irregular 

 markings. The central portion of the patch becomes studded 

 with the minute perithecia of the fungus. The tissue of the 

 stem underlying each patch becomes brown and dead, the 

 injury extending to the centre of the stem. When a plant is 

 attacked the leaves soon turn yellow, and the whole plant 

 perishes within a short time. 



