72 EELWORMS. 



of plants. The genera Dorylaimus and Aphelenchus also live 

 under similar conditions. Tylenclms and Heta-odera produce 

 the worst diseases. 



These undergo part of their life-cycle in the earth and part in 

 their plant host. 



The three most typical forms are — (1) the "Wheat Eel worm 

 (Tylenelms scandens) ; (2) the Stem Eelworm (T. devaxfatrix) ; 

 and (3) the Beet Eelworm (Heterodera Schachtii). 



The Wheat Eelworm (T. scandens = T. tritici of Bastian). 



Length about one-twelfth of an inch in the male and one- 

 tenth to one-fifth in the female. These minute white or almost 

 transparent Vermes are the cause of a disease, especially in wheat, 

 known as "purples,'' "ear-cockles," or "peppercorns." 



We may often notice in several parts of an ear of wheat 

 that there are in place of the grains dark purplish - hrown 

 galls, having a striking resemblance to a seed of the " corn- 

 cockle plant." On cutting open one of these "galls" the 

 interior is seen to be full of a mass of a whitish-yellow colour, 

 which contains thousands of eelworm larvse, varying from -^th 

 to aVth of an inch long. When these galls are resown with the 

 wheat-seed, the apparently dried-up worms come to life, and the 

 eelworm larv* enter the soil. On the sound seeds germinating, 

 the larvae make their way to the nearest rootlets of the seedling 

 plants, and then bore between the leaf-sheath and the haulm, or 

 in the terminal bud. As the plant grows they ascend, and 

 quickly get into the ear and swell out the ovary (the future 

 grain), whose walls become first dark -green and then purplish- 

 brown. From sixteen to twenty are found in the lowest flower 

 of the ear, ten to twelve in the next, and from four to five in 

 the topmost blossoms. As soon as they enter the flower the 

 worms become sexually mature, and then lay from six hundred 

 to sixteen hundred ova, which give rise to the larvre we find in 

 the ear-cockle later on in the year. 



