SUGGESTIONS FOR RELIABLE HYPOTHESES 187 



as with the gigantic flower Rafflesia Arnoldi which 

 is seated immediately upon the roots of the host plant. 

 Such extreme Parasites can no longer fulfil the main 

 task of plants viz. that of assimilation (i.e. to form 

 organic material from the carbonic acid of the air and 

 the water and salts of the soil). By the formation of 

 the most diverse organs, with which they form con- 

 nections with the host plants, they permeate these and 

 also in most cases destroy them. 



A convincing proof cannot certainly be produced 

 that the parasites pursued formerly another and inde- 

 pendent mode of life. Yet, also among the plants, 

 we have some indications leading to this assumption. 

 Many so-called semi-parasites like Euphrasia, Thesium, 

 etc., possess green leaves and true roots, but c they 

 attach themselves by discs or wart-like outgrowths 

 to the roots of their host plants/ * from which they 

 draw directly water and nutritive salts. It can well 

 be assumed that the opportunity afforded by coming 

 in contact with other roots when seeking for water 

 gave the impulse to the formation of sucking apparatus. 

 An attraction of the roothairs towards water, whether 

 in the soil itself or in the roots in the soil, must be 

 assumed, since the finest rootlets have always given 

 the impression that they sought for humidity. What, 

 therefore, was formerly caused by chance namely the 

 formation of sucking apparatus in the said semi-para- 

 sites may gradually become a permanent tendency 

 in the plants, so that thus the Euphrasia, which cannot 



1 Strasburger : Lehrbuch, p. 42. 



