TEANSLOCATION OF NUTRITIVE MATERIALS 225 



before it can be restored. To prevent this there should be 

 a storage of food close to the seat of its consumption, so 

 that, with the awakening need, the required supply may be 

 at hand. 



This temporary storage of food must play an important 

 part in the metabolism of an organ whose vital processes 

 are subject to such numerous and often rapid checks as 

 befall young stems, leaves, and roots. Still more necessary 

 is it to the floral and fruiting organs during the time of 

 their maturing. 



We have seen again that plants set apart particular 

 structures for periods of longer quiescence, especially in 

 connection with their reproductive processes. Seeds may 

 remain for several years without germinating, and they 

 generally do so at least for months. The embryo in the 

 seed is, however, ready to resume its growth as soon as all 

 conditions are favourable. It is evident that it is in a 

 practically helpless condition with regard to the manufac- 

 ture of food, and it must depend upon a previously stored 

 supply for the resumption of vital activity. The parent 

 plant must, therefore, store quantities of its manufactured 

 products in or about the embryo in the seed, stores with 

 which it will itself have no further concern, but which will 

 be altogether the property of the new organism. The same 

 thing is seen to be the case with tubers, bulbs, and other 

 organs of vegetative propagation. 



A condition intermediate between the two we have so 

 far described is presented by the large fleshy roots and 

 rhizomes of biennial and perennial plants. For an illustra- 

 tion we may consider an ordinary carrot or beetroot. 

 Though these plants propagate themselves by the prepara- 

 tion of flowers, fruits, and seeds, they do not enter on this 

 task during the first year of their lives. During this time 

 they are in full foliage, and their constructive processes 

 are at their best. They store in their roots a large amount 

 of the food so prepared, and these towards the close of the 

 first year's vegetation become enormously swollen by the 



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