DISEASES OF VARIOUS CROPS 



1545 



Table II. — Pentosan and Methyl- Pentosan Content of Sotmd 

 and Rotted Quarters of Potatoes {percentage of pentosans, leet iveight). 



It should be noticed, on the other hand, that the fungi grown in potato 

 extract produce as much pentosan as methylpentosan, so that the given 

 quantities in the table represent the difference between the amount of pen- 

 tosan destro3'ed and the amount built up b}^ the fungi. 



The crude fibre is a mixture of compounds, among which are some of 

 the cell wall constituents, including cellulose. The distribution of the crude 

 fibre is not as uniform as that of the pentosans. It is 3 ^/g to 5 times as 

 abundant in the cortex a? it is in the inner part of the tuber. Parasitic 

 fungi raise the percentage of crude fibre a little, although the differences in 

 question are alwa^'s small. 



The substances which give mucic acid when boiled with the proper 

 concentration of nitric acid are considered in this paper as galactans. The 

 effect of Fiisariiim on these substances is shown in the following table : 



Table III. — Galactan Content of Sound and Rotted Quarters of Potatoes. 



All the species of Fusarium examined gave practically the same results. 

 It is worthy of note that the grains of starch remain intact, while the 

 monosaccharids and disaccharids are attacked by the fungi, although they 



