558 DISEASES OF CULTIVATED PLANTS 



with the seed they become soft, and the eelworms escape into 

 the soil and make their way to the sprouting wheat, and 

 insert themselves under the leaf-sheaths, where they remain 

 until the ear commences to form, when they enter the soft, 

 young grain, and a gall or * ear-cockle ' is produced. 



Grain containing ear-cockles should not be used for seed. 

 Some of the infected grains can be removed by screening the 

 seed ; or if the infected seed is placed in water, so that the 

 liquid is a little above the grain, the light ear-cockles will 

 come to the surface, and can be skimmed off. The grain 

 should be stirred up, so as to allow all the diseased ones to 

 come to the surface. 



Bastian, C., Trans. Linn. Soc., 25, p. 87. 



Ormerod, E. A., A Manual of Injurious Insects^ p. 104. 



Beet-sickness, caused by Heterodera satMi (Sebum.), proves 

 injurious to the sugar beet on the Continent ; mangold, 

 turnips, rape, cabbage, roots of some cereals and leguminous 

 plants, and weeds of various kinds are also attacked. When 

 a beet is attacked by eelworms the leaves become flabby, 

 yellow, and soon die, the top of the root changes to a blackish 

 colour, and the whole soon decays. The smaller rootlets 

 bear numerous knots containing eelworms. 



Kiihn, a German scientist, has proposed the partial clearing 

 of the land from eelworms, so that a fairly successful crop of 

 beet may be secured, by means of a 'trap crop.' Summer 

 rape has proved to be most successful, on account of its quick 

 growth and large spread of root. Success depends on the 

 prompt removal of the rape when the largest number of 

 eelworms have entered the tissues of the root, and before a 

 new brood is produced. 



Lime, sulphate of potash, and salt have respectively been 

 found to arrest the progress of eelworms in the soil. 



Fern eelworm (Aphelcnchus olesistus, Ritzema Bos) forms 

 deep brown blotches on the fronds of various ferns Pteris 

 cretica, Aneimia collina, Lygodium volubile, Adiantum capillus- 

 veneris, Pteris Droogmantiana, and other species. The shape 

 of the brown blotches is determined by the venation of the 

 frond. Where the veins are more or less parallel, as in 

 Lygodium, the blotches take the form of narrow, parallel 

 streaks, whereas when the veins anastomose irregularly the 

 blotches are more or less angular. This arrangemen is due 



