432 DISEASES OF CULTIVATED PLANTS 



cultivated peas, forming rather large, irregularly shaped, pale 

 spots, bounded by a dark line, and studded with the minute, 

 dark perithecia. Similar spots are sometimes present on the 

 leaves and stem. The variety known as the ' edible podded ' 

 or ' sugar pea ' is very susceptible to this disease. 



The spores escape from the perithecia as reddish tendrils 

 which soon become pale ; spores hyaline, oblong, i-septate, 

 slightly constricted, 14-16x4-6 //. 



Spraying with dilute Bordeaux mixture, on the first appear- 

 ance of the disease, checks its extension. 



Walnut leaf spot. The living leaves of Juglans regta are 

 often disfigured by the appearance of roundish, greyish-brown 

 spots with a darker margin, which vary in size from i mm. to 

 i cm. in diameter, due to Ascochyta juglandis (Boltshauser). 

 These diseased patches become dry and fall away, leaving holes 

 in the leaf. Under a lens minute, lighter points can be seen on 

 the upper surface of the dry patches ; these are the mouths or 

 openings of the minute, globose perithecia, which are sunk 

 in the substance of the leaf. The spores are oblong, i -septate, 

 often constricted at the septum, the two cells are often of 

 unequal size, 10-13x4-5 /u. 



Boltshauser, H., Zeitschr. Pflanzenkr., 8, p. 263 (1898). 



Ascochyta dianthi (Berk.) forms rather large, somewhat 

 circular pale patches, usually bounded by a darker margin, 

 and studded with the numerous, minute, dark perithecia, on 

 living leaves of various species of Lychnis, Dianthus, and 

 Saponaria, both wild and cultivated. Spores narrowly 

 elliptical, or with the widest part above the middle septum, 

 hyaline, 14-17x4-5 /* 



The general appearance of the diseased spots resemble 

 those caused by Heterosporium echinulatum (Cke.), but a 

 microscopic examination of the fungus at once determines to 

 which of the two the disease is due. 



Ascochyta Cookei (Massee) forms blotches on living leaves 

 of Lychnis vespertina that are indistinguishable from those 

 caused by Ascochyta dianthi, but the spores are cylindrical or 

 with a slight suggestion of being clavate, i-septate, hyaline, 

 36-42 X 5 p. 



Ascochyta brassicae (Thum.) forms numerous large, usually 

 circular, greyish dull patches on living cabbage leaves ; the 



