No. 4.] 



PLANT DISEASES. 



23 



plant, its development as an individual, and, indeed, its 

 origin and history as a cultivated race. 



It follows, then, that the important thing from the practi- 

 cal standpoint is to study all the maladies of each crop, both 

 in relation to each other and in relation to the development 

 and history of that particular crop. To make this the more 

 clear, let us at once consider and compare the respective dis- 

 eases of two of the commonest of our cultivated plants, — 

 the apple and the potato. We will first enumerate their 

 maladies that we may clearly classify and compare them ; 

 then proceed to a discussion of the relation of these to the 

 history and development of the respective plants. 



Some of the Commonest Diseases of the Potato, classified as to Cause. '^ 



Name op Disease. 



Cause. 



1. Scab of the tuber, .... 



2. Late blight of leaves (often q^lled 



" nist," and rot of tubers) . 



3. Early blight, or leaf spot, 



4. Leaf blotch, 



5. Black-leg and possibly some rot, . 



G. Bacteriosis, wilt of tops and rot of 

 tubers. 



7. Internal browning of the tubers, . 



8. Sun-scald of leaves, 



9. Tip-bum of leaves, .... 



10. Arsenical poisoning, 



11. Colorado beetle, .... 



12. Flea beetle 



1.3. Grasshoppers, , . . . , 

 14. Stem borer or stalk weevil, . 



A fungus, — Oospora scabies. 



A fungus, — Phytophthora Infestans. 



A fungus, — Alternaria solani. 



A fungus, — Cercospora concors. 



Either fungus, — Rhizoctonia (?) or 



bacterial, — Bacillus (P) . 

 Bacteria, — Bacillus solanacearum. 



A physiological disorder, probably as- 

 sociated with improper water supply. 



A physiological disorder, due to sudden 

 excessive evaporation. 



A physiological disorder, due to long- 

 continued dry heat. 



A physiological disorder, from improper 

 use of poisons. 



An insect, — Doryphora decemllneata. 



An insect, — Crepidodera cucumeris. 



Insects, — Melanoplus sp. 



An insect, — Trtchobaris trimotata. 



• In connection with the discussion of the above maladies, the speaker exhib- 

 ited an illustrative series of specimens and charts, and mcidentally discussed the 

 specific remedies. 



