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66 PARASITIC PLANTS [CHAP. 



two suckers help mechanically to fix the plant. 

 Their cuticle presents fine indentations, which 

 mould themselves upon the corresponding 

 asperities, fitting into depressions of the cuticle 

 between the adjacent cells of the host. And they 

 adhere still more firmly by means of a gummy 

 secretion. The means by which the root-sucker 

 or haustorium penetrates the host is mainly by 

 pressure, leverage being secured by the close- 

 ness of the coils together with the superficial 

 adhesion mentioned above. Besides this the 

 central epidermal papillate cells dissolve a 

 passage and absorb the nutriment which is con- 

 veyed to the root immediately below them. As 

 they are not the true sucker (as in the 

 Euphrasiece), this epidermal sucker is called the 

 " pre-haustorium." 



Experiments show that although no chlorophyll 

 is visible in dodder as a rule, it can be induced 

 to form it ; for if short lengths be cut off a 

 branch, the failure of sufficient nutrition in 

 the supply of food from below, necessary for 

 the formation of haustoria, being removed is 

 now compensated for by the immediate forma- 

 tion of chlorophyll. Similarly, if the dodder 

 be attached to a feeble host, or to one 

 which cannot nourish it properly, it puts on 

 chlorophyll so as to be more independent of 

 its host. When, however, fresh haustoria 

 have been made on a fitting host, then the 



