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lunga, ea,rboiiic aci4 and otter gj^sea, Th,us, what is of no seJjvice to 

 the one, is essential to the other, and vice versA. Plants, as thej 

 feed, fit the air for the respiration of animals ; animals, as they 

 breathe, yield up to the atmosphere the ingredients needed for the 

 food of plants. The following is a simple mode of proving ,the 

 emission of oxygen gas from plants : — Take a few leaves, place theBa 

 in a tumbler half filled with water, invert over the mouth of the 

 tumbler a funnel of glass,closing its aperture by a small cork, and 

 place the apparatus in a window exposed to the sun. Shortly bubblo? 

 of gas will be observed on the leaves ; the, gas so formed will 

 accumulate, and ultimately fill the funnel. If now the cork be 

 removed, and a lighted match be applied to the end of the tube, the 

 match will burn with increased brilliancy, or if its flame be previously 

 put out, and the wood be in a, glowing state, it will again burst into 

 flame when placed near the aperture of the funnel, thus proving 

 ^he existence of oxygen gas. At night, or if exposed to darkness, 

 the leaves cease to feed ; but as they continue to breathe they set free 

 carbonic acid, and, to some extent, therefore, render the air impure 

 for animal respiration. 



" As a result of the interchange of gases, of which we have been, 

 speaking, growth, the formation of new tissues, and the production of 

 various secretions, &c., take place. It is the green colouring matter 

 of the leaf, the Moropliyll, which is the chief p.gent in the breaking 

 up of carbonic acid, the setting free of oxygen, and the fixing of the 

 carbon under the influence of sunlight. It is supposed by chemists 

 that the gradual reduction in the quantity of oxygen may account for 

 the formation of starch, various vegetable acids, and other secretions, 

 containing relatively less and less oxygen, till ultimately, such 

 substances are formed as turpentine, resins, or other sorcalled hydro- 

 carbons, which consist of hydrogen and carbon in admixture, and 

 into the composition of which little or no oxygen enters. 



" The remaining phenomena of plant life may perhaps be best 

 illustrated by continuing our comparison of them with ^hose mani- 

 fested in the Animal Kingdom. Anatomically, there is no line to 

 be drawn between plants and animals ; the lowest plants and 

 the lowest animals are so much alike, that it often happens that the 

 naturalist is unable to say to which group a particular organism may 

 belong. Physiologically, however, there are differencess, as w^ shall 

 now attempt to show. Regarded as living beings, both plants and 

 animals' feel, feed, digest, breathe, grow, move, and increase in 

 numbers. It is in their mode of fulfilling these functions that the 

 chief differences between the two kingdoms consist. 



" Plants feel — they respond to stimulus. They may not be able to 

 communicate their sensations as some animals do ; but many of the 

 latter are not a whit more communicative on this point than a sea- 

 weed. We, as members of the Animal Kingdom, feel ^he impact or 

 contact of other substances. Light, heat, cold, electrical disturbanq^, 

 chemical substances, all make lis feel ; and if the sensation be of a 

 disagreeable nature, we get away from the source of irritation as fast 

 as we can ; but if the sensation be jjeasant, we endeavour to repeat 

 it. In the ease of plants the great stimuli are light and heat. These 

 exert a powerful influence on the protoplasn;!, as has been shown again 

 and again. Tho protoplasm , of plar^ts, and the ' sarcode ' of animals 

 have precisely similar properties. The action of light iii giving rise to 



