Bean Anthracnose 129 



As the acervuli become older, long-pointed, brown, septate hyphae 

 (setae) are produced here and there among the conidiophores and often 

 in a ring near the margin. These range in length from 30 to 90 n. Some 

 taper evenly to a point from a base 8 to 10 fx wide; others have a bulbous 

 base, which Beach (1892:319) reports as being often many-celled; many 

 do not taper evenly but are swollen near the septa. They vary in number 

 from a few to as many as twenty in an acervulus (Plate I, 2). Black 

 stromata made up of dark-colored hyphae are produced on the surface of 

 dead areas of leaves spotted by anthracnose and on the surface of dry 

 pods, and these invariably support setae. Setae are abundantly formed 

 also in old agar and bean-pod cultures. Frank (1883 b: 517) found them 

 in lesions on bean pods, and describes them as sterile, brown, hair-like 

 appendages of the fungus. 



The fungus in the seed 



The fungus passes the winter in the seed as mycelium lying within 

 the cells in a more or less dormant condition. It may be confined to 

 the cells of the seed coat, but in badly diseased seeds it occurs in the 

 cells of the cotyledon. It exists there as vacuolate, closely septate, 

 hyphae, from 3 to 5 m in diameter, which are wound about in the 

 cells or extend diagonally across into other cells. It may occasionally 

 be found as a cobwebby growth between the seed coat and the 

 cotyledon, or even between the two cotyledons within the seed. Frank 

 (1883 b: 520) found spores produced in lesions of the seed, Scribner (1888) 

 says that spores and basidia may be found between testa and embryo, 

 and Halsted (1892:285) found them borne in the cavity between the 

 cotyledons of the diseased dry seed. Halsted called attention to the 

 rapid growth of the fungus and to the production of spores on the diseased 

 seed when it is placed under a bell jar. Edgerton (1910:10) notes that 

 acervuli are often present on the surface of the spots and between the 

 cotyledons, and finds peculiar closed pycnidia-like bodies buried some 

 distance beneath the surface of the bean. 



Gain (1898) has shown that the density of attacked seeds may be lowered 

 as much as 4.7 per cent. Muncie (1917:37) states that badly affected 

 seed will remain on the surface of a solution of sodium nitrate of given 

 concentration, while slightly affected and clean seed will sink in it. 



