12 ELEMENTS OF BOTANY. 



often be called plants with as much propriety as animals, 

 and animals with as much propriety as plants, on account 

 of the simplicity of their structure and the few characters 

 they present, upon which a systematic classification may be 

 based. It has been proposed to form another Group, 

 called the Protista, to receive these low organisms ; the 

 higher representatives of the Vegetable and Animal King- 

 doms are readily distinguished by many anatomical and 

 physiological characters. 



Plants feed on mineral or inorganic substances. Animals 

 derive their food from plants. Many of them, as the her- 

 bivorous animals, feed exclusively on vegetation. Carniv- 

 orous animals, devouring the vegetable-feeders, depend no 

 less really though indirectly on plants for food. 



Plants in general consume carbonic dioxide, and liberate 

 oxygen. This is not true, however, of the parasitic plants, 

 called Fungi. Animals consume in respiration oxygen, 

 and liberate carbonic dioxide. The two kingdoms are 

 thus mutually dependent. 



The surfece expansion for absorption, etc., is very exten- 

 sive in case of both plants and animals. In case of plants, 

 however, it is mainly external, as the surface of the roots, 

 rootlets, rhizoids, stems, and leaves ; in case of animals it 

 is, in the main, internal, as the alimentary canal, the vas- 

 cular and respiratory vessels, etc. 



Plants possess chlorophyll, that is, green coloring matter, 

 by reason of which they are able to convert the inorganic 

 food into organic matter. Fungi and other parasites and 

 saprophytes are destitute of chlorophyll, and these plants 

 appropriate to their own use the food assimilated by chloro- 

 phyll-bearing plants. Animals, with the exception of a 

 very few low forms, do not possess chlol-ophyll. 



