80 BEET, SPINACH, AND CARROT DISEASE. 



where the large leaves were totally covered by a living 

 mass of these creatures. In some plants portions only of 

 the leaf were destroyed ; in others more extensive mis- 

 chief was effected ; and in those plants where the malady 

 had proceeded still further, the gangrene was propagated 

 from the leaf down the stalk, and so on to the crown of 

 the root, which last finally became affected. The insect 

 destroys leaf after leaf, till in some cases the entire plant 

 is killed. The growth of the plant is of course materially 

 interfered with by the stripping off of its leaves, and in 

 several instances I observed that the root was totally 

 rotten. When the root is rotten the disease appears mostly 

 close to the spiral vessels ; and, from the number of these 

 vessels in this plant, the whole speedily becomes affected. 

 (Plate vii., fig. 6.) 



(321.) In this plant I observed a fact which I have 

 noticed in many other instances ; viz. that the greatest 

 amount of mischief is produced in the plant at that period 

 of its growth when we may expect fibre to be deposited. 



(322.) For this reason the whole plant seemed always 

 to be more seriously deranged when it had prematurely 

 run to seed ; the small leaves of the stem were more 

 seriously destroyed ; the stalk was more injured, and the 

 whole plant died. 



(823.) I do not pretend to have counted the number of 

 the vastator which may be found occasionally on a single 

 plant ; but I should say, confidently, that not less than 

 30,000 or 40,000 may be sometimes found on a large 

 specimen. 



(324.) There is another species of Aphis, a little black 

 rascal, which also infests this plant, but 1 have not found 

 it to a very great extent. 



