76 DISEASES OF CULTIVATED PLANTS 



Lousewort. The two British species, Pedicularis palustris 

 (L ),and P. sylvatica (L.) are common and generally distributed. 

 The flowers are rose-pink, leaves much divided. The former 

 grows in bogs and marshes, and has a solitary, branched, 

 erect stem. P. sylvatica grows on wet heaths and in damp 

 pastures and thickets. Stems numerous, the central one 

 reduced to a flowering stem, the others elongated and 

 decumbent or prostrate. 



Cow- wheat. The four British species have slender, wiry, 

 simple or slightly branched stems, opposite long, narrow, and 

 entire leaves, and leaf-like floral bracts which are often 

 coloured. For Afelampyrum pratcnse (L.) the corolla is pale 

 yellow; in Af. sylvatiatm (L.) the corolla is deep yellow; in 

 M. cristatum, yellow, tipped with purple, and in M. arvense 

 (L.) the corolla is rosy with a yellow throat. 



The species occur in woods, copses, heaths, and pastures. 



According to L. Gautier, M. pratcnse is quite specialised 

 in its parasitism. It prefers the roots of trees, especially 

 beech, the roots of which are well provided with mycorhiza. 



Yellow rattle {Rhinanthus crista-galli^ L.) is a very com- 

 mon and widely distributed plant in meadows, damp pastures, 

 and marshes. Stem wiry, square, six to eighteen inches high, 

 leaves opposite, long and narrow, toothed ; flowers bright 

 yellow, in the axils of opposite leaf-like bracts. Capsule 

 orbicular, flattened, containing a few rather large, orbicular, 

 compressed seeds which become free and rattle in the 

 capsule when the plant is shaken, hence the popular name. 



Bartsias. Annual or perennial weeds. Parts/a odontitis 

 (Huds.), a branched plant with wiry steins, narrow, serrate 

 leaves, and pink flowers in secund or one-sided spikes ; is 

 generally common in fields and waste places. />'. viscosa (L.) 

 is a viscid plant, corolla yellow. A. alpina (L.) has dull 

 purple-blue flowers, and is more at home in the arctic region 

 than in Britain. 



Eyebright. -The only British species (Euphrasia officinalis, 

 L.) is very common and generally distributed in meadows, 

 pastures, heaths, etc. Stem wiry, much branched, four to ten 

 inches high, leaves small, toothed, floral bracts leaf-like; 



