THE FUNGI WHICH CAUSE PLANT DISEASE 623 



tapering, obtuse, basally dark-brown, slightly constricted at the 



septa, 5 to 9 times cross-septate and 0-5 times longitudinally 



septate. 

 It causes injury on carnation leaves and stems. 

 A. solani (E. & M.) Jones & Grout. '"• ^''' '"'-'" 

 Spots brown, circular to elliptic, concentrically zonate, amphige- 



nous, irregularly scattered over the leaf surface; mycelium 



Fio. 422. — A. solani, 2, spores germinating and penetrating the living 

 potato leaf; 5, showing cateuulatiou of spores. After Jones. 



light-brown; conidiophores erect, septate, 50-90 x 8-9 /i; conidia 

 obclavate, brown, 145-370 x 16-18 fi with 5 to 10 transverse 

 septa, longitudinal septa few, conidia terminating in a very long 

 hyaline, septate beak J^ the length of the conidium or longer. 



It causes early blight, a leaf spot disease of potatoes and toma- 

 toes,'*^ and is widely prevalent. It was first described in 1882 in 

 America but is now known to be widely destructive.*'^ On potatoes 

 it was first recorded by Galloway in 1891. In 1891 also Ches- 

 ter '*^ and Galloway **® proved its pathogenicity by inoculations on 



