May 1, 1916 Effect of Fusariufn spp. on Potato Tubers 



193 



cellulose may be present. The distribution of the crude fiber through- 

 out the tuber is not as uniform as that of the pentosans, as is shown by 

 a comparison of Tables XI and XIV. 



Table XIV. — Crude fiber content of the skin and inner part of the potato tuber 

 [Expressed as percentage on both a wet weight and dry weight basis] 



From Table XIV it may be seen that the crude-fiber content of the 

 peeling is ^}4 to 6 times greater than that of the inner portion calculated 

 on a wet weight basis and from 4 to 10 times greater on the basis of dry 

 weight. The inner portion of the potato contains usually a lower per- 

 centage of crude fiber than of pentosans. 



The determinations of crude fiber on the sound and rotted portions of 

 the potato tubers are given in Table XV. 



Table XV. — Crude-fiber content in sound and rotted quarters of potatoes 

 [Expressed as percentage of wet weight] 



Rotted with Fusarium radicicola. 



Rotted with Fusarium oxysporum. 



Potato No. 



37- 

 39- 

 115 



Rotted 

 quarter. 



56 



57 

 40 



Sound 

 quarter. 



54 

 56 

 37 



Potato No. 



177 

 178 

 179 



Rotted 

 quarter. 



O. 71 

 • 73 



Sound 

 quarter. 



0.58 

 .62 

 .62 



The crude-fiber content is always higher in the rotted quarter of the 

 tuber than in the corresponding sound portion, though the difference is 

 not great. As has been mentioned earlier in this paper, the fungus builds 

 up a considerable quantity of substance which is not dissolved in either 

 the acid or alkali used in the crude-fiber determination ; to this is due the 

 rise in the crude-fiber content of the potato during rotting. It is possible, 

 of course, that the fungi may break down the crude fiber of the host plant 

 and build up some similar substance with greater rapidity. From the 

 evidence brought out in these experiments, then, it is impossible to draw 

 definite conclusions. 



The substances in the potato which give mucic acid when boiled with 

 proper concentration of nitric acid are considered in this study as galac- 

 tans. They are present in small quantities in the potato, and the com- 



