THE STOEAGE OF EESEEVE MATERIALS 233 



As the trunk grows older similar stores of food may be 

 detected deeper in the wood. These generally occur in 

 the medullary rays, either those which are the continua- 

 tions of the primary ones, or others which are formed 

 apparently for the purpose under discussion. These stores 

 are especially for the nutrition of the more deeply placed 

 wood-cells, when the ordinary constructive processes are 

 in abeyance, as in the winter-time. 



Transitory stores may also be detected near the growing 

 points of the axis. These are due to intermission of growth 

 and a consequent sudden cessation of the demand upon the 

 translocation stream. The latter, instead of being diverted 

 at once from the region to which it had been travelling, 

 deposits in a suitably stable form the food which would 

 have been consumed had not the check in the demand 

 occurred. The supply is consequently ready to hand as 

 soon as growth sets in again. 



Deposits of reserve materials can be observed near the 

 extremities of twigs as winter approaches. The output of 

 the young leaves in the spring is greatly facilitated by the 

 occurrence of such temporary storage. It is possible by 

 appropriate pruning to influence to a considerable extent 

 the locality and the extent of such deposition. This is of 

 very common occurrence in horticulture, the nature of the 

 pruning having in this way a very considerable influence 

 upon the development of floral or foliage shoots. 



Transitory deposits of food take place also in the floral 

 organs. In many flowers which have long succulent styles, 

 which must be perforated by the pollen tubes on their way 

 to the ovules, there may be observed very frequently a 

 deposition of food in the tissue of the style at the time 

 when the germination of the pollen grain takes place upon 

 the stigma. The food is then usually stored in the paren- 

 chymatous tissue which surrounds the vascular bundles of 

 the organ. 



Many of these reservoirs show by their structure that 

 they are only intended to compensate for regular or 



