453 



CHAPTEE IX. 



DIGESTION OF RESERVE MATERIALS. 



We have noticed in following the deposition of reserve materials 

 that their permanent form differs from that which they assume 

 for purposes of transport. They are generally insoluble, and almost 

 always indiffiisible, whereas they travel in the form of soluble, 

 diffusible bodies. The removal of them from the seats of storage 

 takes place at times dependent on the resumption of activity of 

 growth or development ; and as this removal is dependent upon 

 the same methods of transport, they nnist undergo a process 

 which, from analogy with similar processes in the animal body, 

 may be described as digestion. They must, after such treatment, 

 be presented to the protoplasm of the growing cells in much the 

 same form or condition as that in which they were first con- 

 structed from the simple bodies absorbed. 



Tliere is no special region in the plant where digestion takes 

 place. It may be looked for in any cell in which any form of 

 reserve material is deposited. 



We have seen again that in a few rare cases nitrogenous 

 material is absorbed into the plant body through certain leaves 

 or modified foliar organs. Tlie insectivorous plants are 

 materially assisted in their growth by capturing and digesting 

 various insects. Drosera does this by means of its sticky leaves, 

 which are furnished with peculiar outgrowths, which bend over 

 and imprison any small insect w^hich alights upon them. The 

 leaf is covered with a sticky or glutinous secretion, which is 

 poured out from these so-called tentacles, and the insect becomes 

 entangled therein. The tentacles then close over the insect and 

 emit a fluid which has the property of digesting the dead bodies so 

 imprisoned, rendering the nitrogenous matters capable of absorp- 

 tion by the leaf tissue. Dioncea imprisons any insect visitors 

 by a different mechanism, and digests them by a similar secre- 

 tion. Many other plants have a similar power. Some plants, 

 such as Ne2)eutlies and Sarracenia, are furnished with large 

 pitchers, which are modified leaves. These contain a waterj^ 

 fluid, and insects falling into the liquid are drowned. Their 

 bodies become decomposed by the aid either of a secretion 

 from glands in the leaf, or by the action of bacteria, and the 

 pitcher absorbs into its tissues the nitrogenous products of the 

 decomposition. 



