CHAPTER XIII 



ANIMALS AND PLANTS 



ANIMALS, being incapable of manufacturing organic 

 food themselves, are necessarily dependent, directly or 

 indirectly, upon plants for their supply of food ; but, 

 on the other hand, many plants depend, more or less 

 completely, upon animals for their existence. While 

 these are usually flowering plants, still among the lower 

 forms of plant life many instances might be cited, 

 especially among the parasitic fungi, like the insect- 

 fungi, and some water-moulds. The same may be said 

 of many of the pathogenic bacteria, or disease germs. 



Occasionally insects appear to be useful to certain 

 fungi by scattering their spores. Such fungi offer 

 certain means of attracting insects, either in the form 

 of a honey-like secretion, or their odor. Thus the 

 evil odor given off by some f ungi, especially the Phal- 

 loidere, attracts carrion-loving insects, which carry away 

 with them the spores which are imbedded in a slimy 

 substance exuded by the fungus. 



It is among the seed-plants, however, that we meet 

 with the most obvious adaptations connected with animal 

 organisms. The development of edible seeds and fruits 

 in so many plants is, in most cases, directly referable to 

 such adaptation. Where the seeds themselves are edible, 

 of course a large proportion are destroyed by the ani- 



242 



