TISSUES AND SIMPLE OUGANS. 



147 



plant-life, as, for example, plaut-cliseases produced l)y parasites. 

 There are also minds which cannot understand how such pathological 

 changes can be harmonized with the original perfection of the 

 vegetable creation. Let such direct their attention to the above 

 facts of symbiosis, which show that conditions which at first sight 

 resemble parasitism are in fact l)enefi('ial t(j both i^laiits. Epipliytic 

 and endophytic association of plants does not in all instances bear 

 the stamp of the pathological or unsuitable. Furthermore, it is in 

 perfect harmony with the Christian conception of creation that the 

 arrangements in nature no longer possess their highest perfection. 

 The injurious and pathological has no doubt made its appearance 

 seeondar'dy, and M'as not originally introduced The teleological 

 view of nature is not ol)scured by the erroneous conception of para- 

 sitic phenomena in the plant-kingdom, nor by the narrow affirma- 

 tion that diseases of man cannot be harmonized with the doctrine 

 of the omnipotence of an all-Avise Being. 



There is a very remarkal)le phenomenon of general occurrence, 

 which is doubtless a form of symljiosis, the more correct knowledge 

 of which we owe to various investigators, especially to Frank. 

 This is the inycorh'tsa (fungus- 

 root) of certain trees. In all 

 climates the terminal root-por- 

 tions of certain forest trees, as 

 Ciqndiferfe, Betulacece., Conif- 

 erae^ are covered with hypha' 

 of some fungus (" ectotroi^hic 

 mycorhiza ' ') which pei'form the 

 function of root-hairs and also 

 take up food-substances from 

 the soil. The biological inter- 

 relation has as yet not been ex- 

 plained very satisfactorily. In 

 reference to Fig. 89 it should ^ig 

 be stated that higher magnifica- 

 tions of a longitudinal section 

 shows that the hyphse of the fungus (m, «, m) actually surround the 

 epidermal cells of the root. 



Here also must be added the '' endotrophic " mycorhiza of the 

 EricacecB^ etc., as well as the symbiosis in the swelling of the roots 



89. 



Root-tip of Carpinus Betulus 

 with mycorhiza. 

 (After Frank.) 



