306 BOTAXICAL GAZETTE [april 



9. Diseases in 



ma\ 



cells before they are actually invaded by the parasite. To these 

 may be applied the term necrosis. Subdivision 

 the basis of the part involved, as: 



ga. Cortical necrosis , in which the cortex chiefly is involved; for 

 example, cankers caused by Sphaeropsis, B. amylovorus, and 

 End ot hi a. 



gb. Parenchymal necrosis, in which chiefly the parenchyma is 

 affected, including the greater number of the soft rots; for example, 

 soft rots caused by B. carotovorus, Rhizopus, Penicillium, Phythia- 

 cysitis, Rhizoclonia, Pythium, Phytophthora, Sclerotinia, Botrytis y 



C olletotrichum , and Gleosporium. 



gc. Macular necrosis, in which necrosis is limited to spots, 

 chiefly occurring on leaves. This is divided into (1) macular 

 necrosis with abscission (the "sho thole" diseases caused, for 

 example, by Cylindrosporium and Marssonia); (2) macular 

 necrosis without abscission (chiefly the leaf spots, caused, for 

 example, by Pseudopeziza, Entomosporium, Macros porium, Lophio- 

 derma , Gidgnardia [Phyllosticta], Ascochyta, Ramularia, Septoria, 

 Diplodia, Cercospora, Colletotrichum, Gleosporium, Fusicladium, 

 Cladosporium, and Alternaria. 



The following synopsis may make these categories and their 

 interrelations clear. 



I. The parasite living in the sap or in cavities or parts devoid 

 of living protoplasm: (1) embolism; (2) wood rots. 



II. The parasite for the major part of its life drawing its 

 nutriment from host cells that are still living: (3) endocellular 

 parasitism; (4) endocellular haustorial parasitism; (5) epidermitis; 

 (6) intercellular mycosis; (7) myosclerosis; (8) tumor. 



III. The parasite living within host cells or tissues which have \ 

 recently been killed or partially disorganized by it: (9) necrosis; 

 (9a) cortical necrosis; (gb) parenchymal necrosis; (gc) macular 

 necrosis; (gc f ) macular necrosis with abscission; (gc") macular 

 necrosis without abscission. 



There is an apparent omission of hypertrophy and hyperplasia, 

 but I regard these two manifestations as symptoms rather than 

 as definite diseases. 



University of Illinois 



