CHAPTER III. DISTRIBUTION OF FOOD MATERIALS. 239 



reserve food-materials of the plant. Stored away in various 

 parts of the vegetable structure, it is so much capital which the 

 plant may draw upon in case of need, to build up new tissues, to 

 repair losses and wastes, or to carry on the exhaustive work of 

 reproduction. 



The power to utilize starch for the building up of protoplasm 

 is not the exclusive property of the green cells, as is that of the 

 first formation of carbo-hydrate, but it is possessed to a greater 

 or less extent by all the living cells of the plant. Tissue con- 

 struction from starch is also not dependent upon light. A potato 

 will sprout in a dark cellar, and the sprouts will continue to grow 

 until they have exhausted all the reserve food-materials in the 

 tuber ; but when this is done they die, for they cannot, without 

 the aid of the sun's radiant energy, construct new materials ; no 

 new carbo-hydrate can be formed, as we have seen, in the 

 absence of light. 



In addition to the assimilative powers already described, all 

 plants are able to reconstruct living out of dead protoplasm. 

 Fungi appropriate, along with other matters, the dead proteids 

 of the decaying organic substances on which they feed. The 

 Sarracenia and Sundew catch and destroy insects, and nourish 

 themselves by the proteids thus obtained. The benefits derived 

 from the use of manures depends, partly at least, on this power 

 possessed by living cells. Every plant also lays by, for its future 

 needs, certain reserve stores of proteid ; these it re-vivifies as 

 occasion requires, and there are also formed in the plant certain 

 lower forms of nitrogenous organic matters, such as asparagin, 

 leucin, etc., which it is able to convert into living protoplasm. 



Such, in brief, is the constructive work of the plant. 



The Distribution and Storage of Reserve- Materials. 

 Starch, in its ordinary form, is insoluble in cold water, and pro- 

 toplasm, as we have seen, is a colloidal substance, and therefore 

 difficultly diffusible. Both must consequently undergo change 

 and pass into other forms, in order to be distributed to the 

 various parts of the plant, where they are required. The starch 

 granules formed in the chlorophyll-bodies under the influence of 

 light, undergo solution in darkness, and disappear. Probably this 

 solvent process is in continual operation during the day, but, 

 owing to the fact that the formation is more rapid than the solu- 



