THE STOEAGE OF EESEEVE MATEEIALS 241 



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 grow- 

 ing 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 



R 



