NATURE STUDY IX SCHOOLS* 77 



between the two, and belong to neither one nor the 

 other. 



Soms naturalists go as far as to place these plant animals, as they 

 are called, in a separate kingdom by themselves, but as this makes two 

 border lines, where there is probably none, it is far better for us to con- 

 sider these peculiar forms are intergrading species between the animal and 

 vegetable kingdom. 



Here occurs an opportunity to impress upon the pupil's mind, the im- 

 portance of the fact that there are no hard and fast lines in nature, but 

 that all living organisms have at one time, through the operation of the 

 change produced by evolution, intergraded, and that the communicating 

 links between groups from species upward, are often to be found living at 

 the present time. 



THE PRINCIPAL DIFFERENCES BETWEEN PLANTS 



AND ANIMALS. 



Animals move voluntarily in response to certain interior irritable fibers, 

 known in higher groups as nerve fiber. Plants move voluntarily, if at all, 

 probably without response to any inner irritation. 



Animals inhale oxygen, exhale carbon dioxide, while most plants re- 

 verse this process, and inhale carbon dioxide, and exhale oxygen, but 

 mushrooms behave at animals do, a*id exhale carbon dioxide. Among plants, 

 however, it is difficult to understand the stimulating cause of the move- 

 ments of the mimosa, venus fly traps etc. 



Animals reach their maximum size comparatively early in life, when 

 they cease to grow, while plants contrive to increase in size as long as they 

 live. Exceptions to this rule may, however, be found in most fishes and 

 in some reptiles. 



The presence of cellulose in plants and its absence in animsls, is one 

 of the best defined differences between the groups, but cellulose is absent 

 in some of the mushrooms and allied forms of plants. 



