TISSUES AND SIMPLE ORGANS. 



147 



plant-life, as, for example, plant- diseases produced by 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 beneficial to both plants. Epiphvtic 

 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 

 secondarily, and was not originally introduced- The teleological 

 view of nature is not obscured 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-wise Being. 



There is a very remarkable phenomenon of general occurrence, 

 w T hich is doubtless a form of symbiosis, the more correct knowledge 

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

 This is the mycorhiza (fungus- 

 root) of certain trees. In all 

 climates the terminal root- por- 

 tions of certain forest trees, as 

 C//j tlif<>rce* Betiilacem, Conif- 

 er<i<\ are covered with hyphse 

 of some fungus (" ectotrophic 

 mycorhiza ' ') which perform the 

 function of root-hairs and also 

 bike 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 Fm 8 9._ R o t_ttp of Carpinus Betulus 

 be stated that higher magnifica- 

 tions of a longitudinal section 

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

 epidermal cells of the root. 



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

 Ericacem, etc. , as well as the symbiosis in the swelling of the roots 



with mycorhiza. 

 (After Frank.) 



