Sweet Pea Diseases 345 



are attacked by the fungus. If the collapsed seed- 

 lings are allowed to remain on the ground, the dead 

 stems will soon be covered with the sickle-shaped 

 spores of the Fusarium fungus. Eventually the dead 

 tissue rots, attracting small fruit flies, which begin to 

 distribute the spores to different places in the same 

 house. The trouble usually appears in widely sep- 

 arated spots on the bench. These spots, however, 

 quickly spread, involving the entire bed, the plants 

 of which may suddenly assume a wilted appearance. 

 Here and there, however, and in the same bench, a 

 few plants remain alive and keep on growing in 

 spite of the disease. 



The Organism. The mycelium of the fungus is 

 hyaline, septate, and branched. At an early age 

 the hyphsE begin to form chlamydospores. These are 

 round hyaline bodies filled with oil globules and are, 

 formed in the center of the hypha, whereupon the 

 contents of the cell collects into the chlamydo- 

 spores. Usually, the chlamydospores are also borne 

 at the tip end of the hyphffi in chains of twos, threes 

 and even fours. Old cultures are practically one 

 mass of chlamydospores. There are also two spore 

 forms present, which appear as early as the third 

 day in the pure culture. These comprise microco- 

 nidia which are fairly abundant and macroconidia, 

 varying from two, three to four celled. The aver- 

 age form of macronidia is the three celled. Both 

 micro- and macroconidia are hyaline and smooth. 

 In old cultures the macroconidia shrink so that the 

 septa become slightly pronounced. These old ma- 



