330 HOW CROPS GROW. 



substance ranges from 23 to 38 per cent. Previous to 

 blossom, the upper leaves, afterwards the lower leaves, ' 

 are the richest in fiber. In the lower leaves the maxi- 

 mum (33 per cent) is found in the fourth ; in the upper 

 leaves (38 per cent), in the second period. 



The apparent diminution in amount of fiber is due in 

 all cases to increased production of other ingredients. 



2. Fat and Wax are least abundant in the stem. Their 

 proportion increases, in general, in the upper parts of the 

 stem as well as during the latter stages of its growth. The 

 ra,nge is from 0.2 to 3 per cent. In the ear the propor- 

 tion increases from 2 to 3.7 per cent. In the leaves the 

 quantity is much larger and is mostly wax with little fat. 

 The smallest proportion is 4.8 percent, which is found in 

 the upper leaves when the plant is ripe. The largest 

 proportion, 10 per cent, exists in the lower leaves, at the 

 time of blossom. The relative quantities found in the 

 leaves undergo considerable variation from one stage of 

 growth to another. 



3. Non-nitrogenous matters, oflier than fiber, viz., starch', 

 sugars, gums, etc. ,* undergo great and irregular variation. 

 In the stem the largest percentage (57 per cent) is found 

 in the young lower joints; the smallest (43 per cent) in 

 ripe upper straw. Only in the ear occurs a regular in- 

 crease, viz., from 54 to 63 per cent. 



4. The albuminoids, \ in Arendt's investigation, exhibit 

 a somewhat different relation to the vegetable substance 

 from what was observed by Bretschneider, as seen from 

 the subjoined comparison of the percentages found at 

 the different periods : 



PERIODS. 



I. II. III. IV. V. 



Arendt 20.93 11.65 10.86 13.67 14.30 



Bretsclmelder 22.73 17.67 17.61 15.39 



* What remains after deducting fat and wax, albunimolds, fiber and 

 ash, from the dry substance, is here included, 

 t Calculated by multiplying the percentage of nitrogen by 6.33. 



These differences may be variously accounted for. They~ 



