250 STRUCTURE AND VITAL PROCESSES OF PLANTS 



can be seen on the surface of cut branches, on which the growth 

 forms rounded lumps of bark on the cut surface. If the cut is 

 somewhat distant from the axis from which the brapch was pro- 

 duced, the sap cannot rise in the leafless stump, and hence the 

 bark gets dry and dies and the wound cannot be covered over. 



C. Steins as Stores for Food in Reserve. 



The leaves of a plant in active operation manufacture more 

 food than can be used up immediately. The surplus of food 

 is, therefore, laid up for any future emergency. 



1. Storage in Trees. — The storage in trees is generally not 

 preserved in special growths, but in numberless little cells along 

 the way which the descending sap travels, viz., in some cells of 

 the inner bark, as also in certain cells extending from the cambium 

 right to the centre of the tree, through the wood-tissue. These 

 rows of cells, which are called medullary rays, appear as silvery 

 rays when a woody stem is cut through transversely. The food 

 in reserve is used by trees in dillerent ways. 



(a) Some trees, like the Teak, shed their leaves in the dry 

 season. Most of the trees do the same during winter in cold 

 countries. They begin to grow again with the return of the 

 rains here, or of spring there, and are in a very short time re- 

 clothed ivitli their beautiful foliage, as if by a miracle. This 

 wonderful change is only made possible by the trees availing 

 themselves of the ready-made food deposited in their stems, which 

 is, when required again, carried to the buds where the plant 

 has, as if by foresight, prepared the future leaves, and, in some 

 cases, even flowers in miniature, before it dropped its leaves. 



ib) At the time oi Jlowering and fruit-bearimj tlic consump- 

 tion of food is so great that a previous storage of it is an 

 absolute necessity. Some trees do not bring forth fruit every 

 year, perhaps because the amount of food stored in one year 

 does not sutflce and they require several years' storage to pro- 

 duce tlieir seeds. An instance of tliis kind is the shrub 

 Strobilanthes growing on the slopes of the Ghauts and generally 

 flowering after the lapse of seven or twelve years. 



