20 DISEASES OF CROPS. 



Cure. — (1) Before clover leys and oat stubbles are 

 ploughed in, they should be treated with a liberal dress- 

 ing of common salt or quicklime. By this means a large 

 number of, if not all, the nematoids are killed. (2) Kiilm, 

 Oehmichen and others {Biedermann's Centralblatt fur 

 AgricuUur-Chemie, 1882, p. 270) recommend strong 

 manuring with kainit in cases of " clover sickness." 



The "White Worms" of Clover. Professor A. 

 Harker, F.L.S., in Nature, vol. 40 [1889], p. 11, writes 

 that it is most probable that certain members of the 

 Oligochceta,^ and more particularly Enchytrcjeus Buch- 

 holzii, g,ttack the roots and stems of clovers, vegetable 

 marrows, and other plants. This " white worm " is about 

 1| inch long, and is supposed to injure the plants by 

 " sucking the fine root-hairs." The " white worms " appear 

 to like the more or less decayed roots of plants, rather 

 than healthy ones ; although the latter harbour a few 

 specimens. Harker says there is " but little room for 

 doubt that these small OligochcetcB are one cause of the 

 decay of the clover of Eothamsted." 



Prevention. — (1) A good system of draining the land 

 will no doubt lessen the activity of these so-called "white 

 worms." (2) Produce a healthy and vigorous growth by 

 using pure seed and suitable manures. 



The Clover Dodder {Cuscuta trifolii, Fig. 5) is a 

 member of the natural order Convolvulacece, although 

 it is a parasite. Clover dodder is incapable of elabo- 

 rating albuminous and carbonaceous substances from 

 such inorganic materials as : carbonic acid, water, am- 

 monia (or rather nitrates) and certain salts, like the 

 higher plants. 



' The earthworm belongs to this natural order. 



