OTHEK METHODS OF OBTAINING FOOD 207 



grow from seed with fair rapidity, the root of the seedling 



attaining a length of an inch in two or three days. Shortly 



after penetrating the soil, the main root puts out secondary 



branches, which make their way parallel to the surface. 



As they grow chiefly in woods or among herbage, they 



speedily encounter the roots of other plants, and on contact 



being made between one of these root-branches and a root 



of a suitable host, a curious sucker-like body is developed 



at the point of con- 



tact (fig. 99). This is 



a kind of parenchy- 



matous cushion, which 



partly surrounds the 



host, and from the 



inner side of its con- 



cavity certain absorp- 



tion - cells grow out 



and penetrate into 



the former, pushing 



their way until they 



reach the centre of 



the invaded root (fig. 



100). These absorbing 



Organs are Often eiTO- FlG> 100. TAwitm alpinum. PIECE OF A ROOT 



WITH SUCKER IN SECTION. x 35. (After 



neously spoken of as 



roots. They cannot 



properly be so called, as they are developed from the cortex 

 of the rootlet, and not, as root-branches are, from the tissue 

 of the pericycle. They are best spoken of as haustoria, 

 a term which is purely physiological, and carries with 

 it no anatomical significance. 



While the root is setting up this relationship with a host 

 plant, the shoot of the seedling is growing normally. Its 

 leaves and other subaerial parts are well developed and 

 discharge their appropriate functions. The plants would 

 not be recognised at all as in any way parasitic without 

 an examination of the subterranean parts. They absorb 



