Ii6 BOTANY OF THE LIVING PLANT 



seedling also loses on germination before its green shoot is expanded 

 above ground. The question will be whether the activity of Photo- 

 Synthesis is sufficient to make up for the loss by respiration over the 

 whole average day's work. // has been estimated that one hour of active 

 Photo-Synthesis will produce as much starch as would supply a loss by 

 Respiration of about thirty hours. Thus there would be an ample balance 

 on the whole day's work not only to prevent loss, but actually to increase 

 the organic supply. 



For all practical purposes Photo-Synthesis in Green Plants is the 

 source to which the origin of all other organic substances may be 

 referred. This applies not only to the plant but also to the animal 

 body. Any general observer will note the dependence of herbivorous 

 animals upon their plant food, and the preying of carnivorous animals 

 upon them. These are simple cases of physiological dependence. 

 However complicated the steps of such physiological dependence may 

 be, practically all organic life forms a continuous physiological chain, 

 the initial link of which is Photo-Synthesis in the Green Plant. It is 

 a process of deoxidation, and all Organic Life consists in the gradual 

 breaking down again of the products of this deoxidation, till the 

 starting points of carbon dioxide, water, and salts are again reached. 

 A horse eating hay or corn digests its materials and evolves their 

 stored energy in the form of work ; while it gives off CO 2 and water 

 in breathing, as well as urea and other matters which mark steps in 

 the return of the materials of its food to the original sources. 



On the other hand, when a plant or animal dies, the corpse may still 

 contain a quantity of combined carbonaceous material. All of this 

 is ultimately returnable in the course of decomposition to the initial 

 forms of water, carbon-dioxide, and certain salts. Nevertheless there 

 is nothing inherent in organic matter itself that leads to decay. Dis- 

 organisation of the dead body follows only as a consequence of the 

 use of its constituent substances by other animals or plants to 

 sustain their own life. These continue the process of destructive meta- 

 bolism, by which the results of construction tend again to return to 

 their original sources. But under certain circumstances decomposition 

 may be arrested. Any organic material treated so as to exclude 

 organisms that cause decay can be kept indefinitely. All " canned " 

 foods depend for their keeping upon this perfect exclusion. The case 

 is somewhat similar where the bodies of animals or plants are buried 

 in mass under water-borne silt. They may then remain for ages 

 incompletely disorganised, as coal. But when dug up the energy of 

 chemical separation of the carbonaceous material, derived from the 



