ORGANIC CONSTITUENTS. 



25 



TABLE 10. Dry weight of seeds and axes and the fiber found in same when grown for 14 



days in tap water. 



PENTOSANS. 



The amount of pentosans in 100 original seeds is 0.2561 gram. 

 There is a gradual decrease of pentosans in the seeds throughout the 

 15 days, and at the end of that period only from 40 to 50 per cent of 

 the original amount of pentosans is present. This change takes place 

 under all conditions of growth as seen from Tables 11 and 12. In 

 the axes, however, the increase of this substance is quite rapid up to 

 about the ninth day. On the fifth day they contain about one-half 

 as much as did the original seeds, and on the ninth day an amount 

 equal to that of the original seed is present. After that date there 

 is a slight but irregular increase, due possibly to the conversion of the 

 pentosans into fiber. The pentosans are supposed to be produced 

 from sugars and to serve as reserve material. As in the case of the 

 fat, at the end of the fifteenth day there is a somewhat larger amount 

 of pentosans in the axes of plants grown in the nutrient solutions than 

 in the control. According to De Chalmot (ibid.) nitrogen fertilizers 

 cause an increase in the pentosan content of plants, especially in the 

 stems. The results here obtained do not indicate that nitrates form 

 any larger amount of pentosans in the axes of seedlings than is formed 

 by potash or phosphoric acid, the differences between the amounts 

 found in the axes of plants grown in different mediums being too 

 small to warrant any definite conclusions. 



In fact, while a somewhat larger amount of pentosans is found in 

 the axes of seedlings grown in the various nutrient solutions than in 

 those of the control (see Table 11) this is probably due to the larger 

 growth made by the plants grown in the presence of plant food. 

 The actual per cent of pentosans based on the dry matter in the 

 axes is approximately the same in each case, i. e., it varies only 

 within the limit of error. From the tables it would seem that from 

 40 to 50 per cent of the original pentosans of the seed remain therein 

 at the end of 15 days. The other 50 to 60 per cent have been utilized 



