204 



FUNGOUS DISEASES OF PLANTS 



Fig. 77 b. Alfalfa defoliated by 

 the Leaf Spot Fungus. (Photo- 

 graph by H. H. Whetzel) 



Small sooty brown or black spots 

 about -X- inch in diameter are 



1 D 



produced, first evident on the 

 upper surfaces of the leaves (Fig. 

 78). In these spots there appear 

 later in the season the relatively 

 simple, sessile apothecia, which 

 are formed beneath the epidermis 

 and break through at maturity. 

 The spots are often very numer- 

 ous, causing defoliation of many 

 of the leaves by the latter part 

 of summer. These structures are 

 saucer-shaped, flat, and light in 

 color, at first fleshy in texture. 

 The club-shaped asci bear eight 

 unicellular colorless spores in 

 two series, measuring 10-14/i in 

 length. Paraphyses are also pres- 

 ent. The mycelium is very local 

 and confined to the area of the 

 spots. This fungus is very closely 

 related to the species causing a 

 leaf spot of clover, Pseudopeziza 

 Trifolii, and with this species it 

 may be identical. No practical 

 method of controlling this dis- 

 ease has been developed. 



XIV. ANTHRACNOSE OF CURRANTS 

 Pseudopeziza Ribis Kleb. 



Dudley, W. R. Anthracnose of Currants. Cornell Agl. Exp. Sta. Built. 15 : 



196-198. 1889. 

 Klebahn, H. Untersuchungen iiber einige Fungi imperfecti und die zuge- 



horigen Ascomycetemforem. Ill Gloeosporium Ribis (Lib.) Mont, and 



Desm. Zeitsch. f. Pflanzenkr. 16 : 65-83. pis. 3-4. 1906. 

 Stewart, F. C. An Epidemic of Currant Anthracnose. N. Y. (Geneva) Agl. 



Exp. Sta. Built. 199: 64-80. 1901. 



