310 BROOKLYN BOTANIC GARDEN MEMOIRS 



phore bears a single spore. Successive production of spores on the 

 same conidiophore, such as has been described by Miyabe (7) for 

 M. parasiticum Thiim., has not been observed for M. sola?ii. Occa- 

 sionally the spores are borne in chains of two. This may occur quite 

 frequently when the atmosphere above the culture is saturated with 

 water vapor and only a few conidiophores are being produced by a 

 vigorously growing mycelium. It occurs very seldom or not at all in 

 cultures that are sporulating abundantly. The occurrence of spores 

 in chains of two is exceptional for M. solani. The writer has never 

 observed longer chains and is inclined to the view that Duggar (i) 

 is correct in leaving this fungus in the genus Macrosporium rather than 

 to put it into the closely related genus Alternaria as Jones and Grout 

 (5) have done. Duggar 's objection that the catenulate method of 

 spore production has not been seen except in artificial culture does 

 not hold, however, for the writer has more than once observed the 

 spores in chains of two on the potato leaf. M. datiirae when grown 

 under very moist conditions also produces its spores in chains of two. 

 This fungus in rare instances even produces spores in chains of three. 

 Under more normal conditions, however, the spores are always borne 

 singly. As one finds it growing on its host or observes it in pure cul- 

 ture, the catenulate method of spore production is exceptional, and 

 it seems doubtful whether any useful purpose would be served by 

 transferring it to the genus Alternaria. The writer has examined 

 many fruiting cultures of the tomato parasite, but has never observed 

 it producing spores in chains even under very moist conditions. 



Besides usually producing their spores singly, both the early 

 blight fungus and the jimson-weed fungus show other characteristics 

 which seem to put them with the Macrosporiums. They both possess 

 a coarser mycelium than is usual for the genus Alternaria. Their 

 spores are larger and under most conditions are produced in smaller 

 numbers than is common for an Alternaria. Moreover, their spores 

 are normally attenuated into a beak similar to that on the spores of 

 other species of Macrosporium, such as M. catalpae, E. & M., M. 

 cucumerinum, E. & E., M. candatuni, C. & E., M. concentricum. 

 Winter, M. brassicae, Berk., M. porri, Ellis, and M. tomato, Cooke. 

 M. caricinum, one of the four species mentioned by Fries (2) at the 

 time he established the genus, bears spores which are, according to 

 his description, attenuated at both ends. No such beaks are to be 

 observed on spores that are borne in chains. 



Since M. solani, M. tomato and M. daturae are parasitic on closely 

 related plants, they have by some authors been considered identical. 

 Sorauer (9) seems to have had this notion and Duggar (i) states that 

 M. solani "is found not only upon the potato but also upon tomatoes 



