PLANT DEVELOPMENT 17 



annual, which produces seed and dies during the first 

 season, we have first a great developraent of root and 

 loaf, which collect and prepare materials for growth ; 

 next comes the formation of a flower stem; and 

 lastly, the production of flower and seed ; after which 

 the plant dies. 



The materials furnished by the root preponderate 

 in the young plant, which is always extremely rich 

 in nitrogen and ash constituents ; but as the plant 

 matures the proportion of carbon compounds derived 

 from the action of the leaves steadily increases. A 

 cereal crop contains at the time of full bloom nearly 

 all the nitrogen and potash which is found in the 

 mature crop ; the assimilation of phosphoric acid con- 

 tinues somewhat later ; the increase of carbon and 

 silica proceeds as long as the plant is in a green state. 



When seed formation begins, an exhaustion of the 

 other parts of the plant sets in ; starch, albuminoids, 

 phosphoric acid, and potash are transferred from the 

 root, leaf, and stem, and stored up in the seed. If 

 the season is a good one, and the development of the 

 seed fully accomplished, the straw of a cereal crop will 

 be found at harvest to be very thoroughly exhausted ; 

 while in seasons of limited production or deficient 

 maturity of grain, the straw will retain far more of 

 the materials acquired during growth. For the same 

 reason straw cut while the crop is still green is far 

 more nutritive than when perfect ripeness of the seed 

 has been attained. 



With a biennial or perennial crop the case is some- 

 what different. The first development of root and 

 leaf is the same as in an annual ; but towards the end 

 of the summer there is a storing up of concentrated 

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