BOTANY FOR YOUNG PEOPLE. 29 



nightingale loads the air with effluvia pernici- 

 ous to itself, the rose neutralizes the poison in 

 its own bosom, and returns pure air to fts fel- 

 low prisoner. When the bird at length expires 

 of old age, singing its dirge of gratitude, the 

 rosebush withers and dies. 



E. This fable presents the subject in its true 

 light, by showing you that while the plant is 

 really necessary to our existence, it is, in work- 

 ing for us, only subserving its own purposes. 

 The four principal elements of vegetables, are 

 CARBON, OXYGEN, HYDROGEN, and NITRO- 

 GEN. Water is made of the second and third 

 of these, and the atmosphere of the second and 

 fourth. We have seen from w T hat source the 

 Carbon may be derived, so that the facility with 

 which plants can find means of sustenance need 

 excite no surprise ; nor yet that they can live 

 without touching the ground and exist on air 

 and the moisture contained in it. Have you 

 ever seen plants that did this, Laura? 



L. O yes. There are Orchis plants in the 

 hot-house, that look just like butterflies, both in 

 shape and color, which the gardener says live 

 on nothing but air. and that he has not even to 

 water them. 



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