COXDITIONS FOR FOmilXO FLOWER AND SEED. 49 



excess of these, wliich tlioy do ikU require for tlieir own 

 enlargement, goes to tliose parts of tlie plant where the 

 motion of the fiuids or the cell-formation is most active, 

 — viz., to the roots, the leaf-buds, or the extreme points 

 of the roots and shoots ; and, finally, as in the case of 

 summer plants, to the organs of seed-formation, which at 

 the ripening of the seed absorb most of the movable 

 seed-constituents existing m the plant. 



The supply of the incombustible elements of food led 

 to the formation of unazotised matter, a portion of which 

 was used to form woody tissue, whilst another portion 

 remained available for the same purpose. The supply of 

 nitrogenous food caused a corresponding production of 

 nitrogenous matter, so that the protoplasm was con- 

 stantly renewed, and, so long as the chemical process 

 lasted, was increased. 



To enable a plant to flower and bear seed, it would 

 appear necessary in the case of many plants that the 

 activity of the leaves and roots should reach a period of 

 rest. It is only after this that the process of cell-forma- 

 tion seems to gain the ascendancy in a new direction ; 

 and the constructive materials being no longer required 

 for the formation of new leaves and roots, are used to 

 form the flower and the seed. In many plants the want 

 of rain, and the consequent deficiency of incombustible 

 nutritive substances, will restrain the formation of leaves 

 and hasten the flowering. Dry, cool weather favours the 

 production of seed. In warm and moist chmates the 

 cereals sown in summer bear little or no seed ; and on a 

 soil poor in ammonia the root-plants more readily flower 

 and bear seed than on a soil rich in that substance. 



If the normal processes of vegetation require a definite 

 proportion of unazotised and azotised materials in tlie 

 protoplasm which is formed in the plant, it is evident 



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