THE FLOEAL WORLD AND GAEDEN GUIDE. 



127 



earth, fii-e, and water. Modern chemists 

 have proved that there are fifty-six distinct 

 simple substances or elements, each pos- 

 sessing distinct characters and properties. 

 Our object being an inquiry into those 

 which enter into the composition of 

 plants, I shall confine myself to these 

 more particularly. First, we have water, 

 one of the most abundant materials in 

 nature ; it forms from one-half to seven- 

 eights of all animal and vegetable matter. 

 It is not an elementary substance, but is 

 composed of two gases, one of which is 

 called hydrogen, from two Greek words 

 meaning water to generate, or water- 

 former ; the other gas is called oxygen, 

 from two words meaning sourness to 

 generate, or acid-former. These two ele- 

 ments unite in the proportion of one part 

 by weight of hydi'ogen, and eight parts by 

 weight of oxygen, forming nine parts of wa- 

 ter. Here wesee an illustrationofalaw which 

 is the most important in chemical investi- 

 gations, namely, that all bodies combine 

 with each other in certain definite propor- 

 tions, wjiich proportions chemists term 

 their equivalent, or combining nmnbers. 

 Thus, hydrogen combines with oxygen in 

 the proportion of one part of hydi'ogen to 

 eigiit parts of oxygen to form nine parts 

 of water ; so one is the equivalent of 

 hydrogen, eiglit the equivalent of oxygen, 

 aud nine the equivalent of water. This 

 law is universal in its ap])lication to the 

 whole range of existing matter. 



Water at every stage of vegetable life 

 performs an important part, as by its 

 means most of those substances which 

 form the food or nutriment of the plant 

 are dissolved or rendered fit for the 

 growth of the plant. In fact, it is an 

 axiom which admits of no exception, that 

 all substances to enter into combina- 

 tion with, or to be assimilated, by either 

 plants or animals must be in a liquid 

 state. 



The next element which enters into the 

 compositiooi of plants is carbon. Carbon 

 exists in natui-e in a perfectly pure state 

 in the form of the mineral called diamond. 

 It forms a large portion of all vegetable 

 matter. If any part of a plant be heated 

 in a close vessel, it gives off water and 

 other substances, and a black mass is left 

 behind, which we call carbon or charcoal. 

 It is important that we should clearly un- 

 derstand what is the source of carbon. It 

 must have struck you as a mysterious fact 

 when gazing on the gigantic oak, that 

 it has grown from the small acorn. You 

 may have asked whence this enormous 

 accumulation of matter! The acorn, 



planted perhaps an hundred years ago, 

 is found to have accumulated fi'om four to 

 five tons of solid matter. The soil is the 

 same as when planted ; that is, we can 

 trace no apparent loss. Whence, then, is 

 it derived ? From the atmosphere. This 

 leads us to consider what are the consti- 

 tuents of the atmosphere, and in what 

 manner it supplies the carbon to plants. 



The air, or atmosphere, is a transparent, 

 invisible substance, without taste or smell. 

 Viewed in masses, it possesses a slight blue 

 colour ; the beautiful blue tint that per- 

 vades the distant objects in a landscape 

 and the sky are due to the colour of the 

 air. 



The atmosphere is composed of two 

 gases, oxygen and nitrogen ; 100 parts by 

 weight of air containing 23.3 of oxygen 

 and 76.7 of nitrogen. Besides these, the 

 air always contains a small quantity of 

 carbonic acid, ammonia, and water. The 

 quantity of carbonic acid varies slightly, 

 but the usual quantity is one part in 3000 

 jjarts of air. It is this substance or gas that 

 i'ui'nishes plants with carbon. Carbonic 

 acid is composed of carbon and oxygen, 

 united in the proportions of six parts of 

 carbon and sixteen of oxygen. It is formed 

 during respiration in all animals ; in the 

 combustion or burning of any substances 

 containing carbon, such as coal, wood, or 

 almost all materials that burn ; in the fer- 

 mentation of beei', bread, and wine it 

 is also formed largely ; it gives the shai'p, 

 agreeable taste to champagne and other 

 refreshing beverages we drink ; water dis- 

 solves a large quantity of this gas ; it gives 

 the peculiar briskness to spring water, and 

 renders it hard, as it is called. If we 

 place a piece of caudle, or any material 

 that contains carbon, in a bottle and light 

 it, we shall find, after having corked it up 

 to prevent a fresh supply of air, that in a 

 few minutes the light will go out ; it will 

 have decomposed all the air in the bottle, 

 the carbon having united with the oxygen 

 iu the bottle, and formed carbonic acid. 

 The same would take place if we put 

 an animal in the place of the burning 

 candle, as the animal would consume the 

 oxygen in the aii* iu the process of respira- 

 tion. After a short time the animal would 

 die, in the same manner as the candle 

 went out, there being no longer oxygen 

 enough to support respiration. The quan- 

 tity of carbon consumed varies much with 

 the climate and the kind of food, but 

 a healthy man consumes in England from 

 ten to thirteen ounces daily ; so we see that 

 a man exhales from thirty-five to forty-five 

 ounces of carbonic acid daily. That this is 



