RESUME. 141 



leaf to deposit solid matter, and a stem with its tuber to 

 supply nutrition. 



(2.) The potatoe plant, as we cultivate it, is in a diseased 

 or abnormal condition, having great excess of tuber and great 

 deficiency of leaves. 



(3.) The potatoe is employed chiefly on account of its 

 starch and albumen, parts which it derives from the leaf. 



(4.) The plant is subject to death at various parts, or a 

 sort of vegetable gangrene. 



(5.) This death, m the form presented by the present 

 disease, is influenced, but not caused, by heat, light, elec- 

 tricity, moisture, soils, and manures. 



(6.) It is, however, caused by the Aphis vastator, which 

 punctures the leaf, sucks the sap, and destroys the relation 

 between the leaf and the root, thus causing the leaf or some 

 other part of the plant to become gangrenous, or, in other 

 words, to die. 



(7.) The vastator destroys, in the same manner, the 

 turnip, the Swede, the beet-root, the cabbage, the brocoli, 

 the radish, the horse-radish, the various wild solani, some 

 kinds of henbane, the stramonium, the belladonna, the 

 clover, the groundsel, the euphorbia, some sorts of rumex, 

 the mallow, the shepherd's purse, the holy thistle, some 

 kinds of grass, and will live upon wheat, the Jerusalem 

 artichoke, the sweet potatoe, and doubtless many other 

 plants. 



(8.) After the attack of the vastator fungi grow, which 

 growth is probably in many cases materially assisted by 

 the prior attack of the Aphis. 



(9.) Other kinds of Aphides will kill in the same man- 

 ner apple-trees, the hop, the bean, the pea, the wheat, the 



