238 HOW CROPS GROW. 



From Table IX we see that the ratio of Hydrogen to 

 Carbon regularly diminishes as the plant matures ; that 

 of Nitrogen falls greatly from the infancy of the plant to 

 the period of full bloom, then strikingly increases during 

 the first stages of ripening, but falls off at last to mini- 

 mum. The ratio of Oxygen to Carbon is the same during 

 the 1st, 2d, and 3d Periods, but increases remarkably 

 from the time of full blossom until the plant is ripe. 



As already stated, the largest absolute assimilation of 

 all ingredients — most rapid growth — takes place at the 

 time of heading out, or blossom. At this period all the 

 volatile elements are assimilated at a nearly equal rate, 

 and at a rate similar to that at which the fixed matters 

 (ash) are absorbed. In the first period Nitrogen and 

 Ash ; in the 4th Period, Nitrogen and Oxygen ; in the 

 5th Period, Oxygen and Ash are assimilated in largest 

 proportion. 



This is made evident by calculating for each period the 

 relative average daily increase of each ingredient, the 

 amount of the ingredients in the ripe plant being assumed 

 at 100, as a point of. comparison. The figures resulting 

 from such a calculation, are given in 



Table X. — Bretschneider. 



The increased assimilation of the 5th over the 4th 

 Period is, in all probability, only apparent. The results 

 of analysis, as before mentioned, refer only to those parts 

 of the plant that are above ground. The activity of the 

 foliage in gathering food from the atmosphere is doubt- 

 less greatly diminished before the plant ripens, as evi- 

 denced by the leaves turning yellow and losing water of 

 vegetation. The increase of weight in the plant above 

 ground probably proceeds from matters previously stored 



