272 



Journal of Agricultural Research 



Vol. XIII, No. s 



Sections through a lesion in which abundant sporulation occurs show 

 acervuli consisting of closely packed, upright conidiophores, 20 to 60 n 

 tall (fig. 3, E). From the apexes of these conidiophores slightly curved, 

 i-septate spores are borne. The spores are hyalin, finely granular, and 



pjc. ^.—Marssmiina i>anaiioniana: A, Mature spores (X 75°); B, immature spores (X 7So); C, spores 

 swollen and constricted at the septa just previous to germination (X 73°); D, germinating spores on 

 epidermal cells of lettuce leaf, showing method of penetration (X 250); E, cross-section of an acervulus 

 drawn from a photomicrograph ( X 30c). 



contain one or two large oil drops. They are constricted at the septum, 

 and the basal cell usually shows a mark where it was attached to the con- 

 idiophore. The two cells are about equal in size. The spores average 

 about 4 by 17 )li in size. The immature spores lack the septum and are 



