FORMS INJURIOUS TO HUMAN INDUSTRIES 



363 



an earlier section (see vol. ii, p. 222). The Stem Eel-Worm 

 {T. devastatrix) attacks the stems and leaves of rye, oats, buck- 

 wheat, clover, &c., leading to stunted growth, or even killing the 

 plants outright. " Clover sickness " is set up by the presence of 

 this parasite. The Beet Eel- Worm {Heterodera Schachtii, fig. 

 1259) infests the roots of its host- 

 plant, and causes " beet sick- 

 ness ". The related Root-knot 

 Eel-Worm (//. t'adicicold) pro- 

 duces galls on the roots of clover, 

 lucerne, cucumber, tomato, and 

 many other cultivated plants. 



Injurious Animalcules 

 (Protozoa). — Nagana or "fly- 

 sickness" (see p. 241) is the 

 best example of disease result- 

 ing from the presence of para- 

 sitic animalcules in the bodies 

 of domesticated animals. 



Some ailments of cultivated plants are also the result of the 

 attacks of certain Protozoa. One instance is afforded by " finger- 

 and-toe " or "anbury", a turnip disease associated with curious 

 deformation of the roots. It is due to the presence of one of the 

 Fungus- Animals (Mycetozoa) within the tissues (i.e. Plasmodio- 

 phora brassica). 



Fig. 1259. — Roots of Beet, infested by Beet Eel-Wortn 

 [Heterodera Schacktii), enlarged, a shows a swelling 

 containing adult female; B, larvae attacking a root. 



