134 



HUTCHINSON'S POPULAR BOTANY 



* 



FIG. 169. LIVERWORT (Mar- 



chantia polymer pha) , 



Showing the stalked antheridial 



receptacles. 



no flame will live. That the vessel is charged with 

 this gas may be proved in a simple manner. Into 

 another jar pour some lime-water. When carbon 

 dioxide and lime-water are brought together, the 

 former combines with the lime and forms an in- 

 soluble carbonate of lime, which imparts a white 

 cloudy appearance to the liquid. If. then, we 

 next tilt the jar containing the peas over the 

 other vessel, the carbon dioxide, which is heavier 

 than the air, will be poured into the lime-water, 

 and the result just described will be witnessed. 



It would be easy to demonstrate further that 

 the germinating peas have absorbed a volume of 



oxygen nearly equal to the volume of carbon dioxide given out; indeed, 

 the absorption has really preceded the evolution of the latter, and is 

 the cause of it. In other words, the oxygen has found its way into the 

 living cells of the peas, and by decomposing, with the active assistance 

 of the protoplasm, some of the complex carbon-containing compounds, has 

 liberated the carbon dioxide. What is known as oxidation, a burning of 

 organic material, has taken place the very process which goes on in 

 animal bodies, and which is called respiration. The germinating peas 

 have, in fact, been breathing, not through an}- special respiratory 

 organs, as is the case in animals, but breathing nevertheless ; and what 

 is true of the subjects of our experiment is true of the living parts of 

 almost all plants. Respiration is as necessary to vegetable as it is to 

 animal life, and in both the great kingdoms breathing and living may be 

 taken as synonymous terms. True, in certain of the lower forms of 

 vegetation, such as the Yeast-plant (Saccharomycets cerevisice) and Bacteria 

 (Schizomycetes), a process of fermentation goes on which appears to 

 obviate the necessity for respiration : but the exceptions only give 

 emphasis to the rule. In the Algce and Mosses (J/itsci), again, respiration 

 is comparatively feeble : still, they breathe, and whenever a free supply of 

 atmospheric oxygen is denied, the}' are suffocated and die. 



As we ascend the scale of Life, respiration becomes more and more 

 vigorous, and is often attended by a sensible liberation of heat, particularly 

 in certain parts of the plant and at certain periods. For this reason the 

 ^^^^^^^^^^^^^^^^ Soldanellas. a small genus of pretty Alpine 



plants, are able to melt a way through the 



^cas&x*^ F CCCc cccr^ hardest crust of SUOAV, their slender flower- 



stalks pushing upwards to the light and air 

 as effectually as if the}* were so man}* fire- 

 heated awls. 



We may add, before passing from this 

 subject, that in many probably in all 



FIG. 170. SECTION THROUGH PART 



OF THE THALLUS OF LIVERWORT, 



Showing a stomate and air chamber. 



