200 Dynamic Theory. 



and so the animal is more or less active, and keeps his wits about him 

 to the end of his days. But the Sacculina andthe Tse nia are like me- 

 chanics whose work is done by machinery better than they could do it 

 themselves. They are deprived of their function, and if another is not 

 developed they are forced to become parasites or tramps. 



CHAPTER XXVI. 



FUNGI. 



In order to understand more fully the relationships between the ani- 

 mal and vegetable kingdoms and the intimate nature of the dependence 

 of the former on the latter, a study of parasitic vegetation, especially of 

 fungi and ferments, is essential. Vegetable parasites, like the animal 

 parasites, exist in every degree of dependence on their host, and with 

 every degree of reduced or lost functions and anatomical structure. 



The parts of a complete plant are such as should enable it to take its 

 nourishment direct from the mineral kingdom and elaborate it into 

 food, or have it done in its own organism. These parts, in terrestrial 

 plants, consist of roots to take up moisture, with carbonic acid, am- 

 monia and various minerals ; of stems with variously formed cells and 

 ducts for the passage and storage of juices and nutriment ; of leaves 

 furnished with pores for the exhalation and inhalation of moisture, and 

 with chloroph}4 cells for the decomposition of carbon dioxide. The 

 root also by its penetration into the soil makes a firm support to the 

 structure, and gives it a local habitation. The essential normal activ- 

 ities of such plants are chiefly to take from the carbonic acid of the air 

 its carbon, which is elaborated into starch in the chlorophyllian cells of 

 the leaves, and sent thence into the roots and stem to be further modi- 

 fied, digested and assimilated, and to draw moisture and nitrogenized 

 matters through the roots. There are many plants not possessed of 

 either roots or leaves but which nevertheless accomplish substantially 

 the same purpose with simple substitutes for those organs. But there 

 are likewise many plants in which some of these essential parts are 

 wanting, and which nevertheless have no substitute for them. These 

 are the true parasites, and they depend upon other plants to perform 

 for them the functions that they are unable to perform for themselves. 

 Like the animal parasites they never lose their reproductive functions. 

 On the contrary, their parasitism taking off the burdens of the elabora- 

 tion and digestion of food, and the formation of the organs necessary 

 for those functions, nearly the whole of the stolen resources of the para- 

 sites may be devoted to their reproduction. Consequently we find that 

 the reproductive spores of fungi are inconceivably numerous. 



