May 1. 19x6 Efject of Fusariuw, spp. on Potato Tubers 



191 



on the constituents of the cell wall was considered of especial interest. 

 The substances studied in this investigation which may be considered 

 to be, in part at least, components of the cell walls are the pentosans, 

 crude fiber, and galactans (5). Inasmuch as the fungi apparently do not 

 affect the skin in rotting the potato, it was considered of interest to find 

 out the relative distribution of the pentosans and crude fiber in the skin 

 and inner portion of the potato. For these analyses the potatoes were 

 peeled as thinly as convenient and determinations made on the weighed 

 peeling and inner portion separately. The results of the pentosan 

 determinations are given in Table XI. 



Tabi^E XL — Pentosan content of the peeling and inner portion of potatoes 

 [Expressed as percentage of pentosans, wet weight] 



Potato No. 



116 

 133 

 134 



Skin. 



O. 62 



.88 

 .80 



Inner 

 portion. 



0.28 

 •39 



•47 



140 

 163 

 164 



Skin. 



02 



72 

 07 



Inner 

 portion. 



©•59 



• 36 



• 50 



When the pentosan content is calculated as wet weight, it is about 

 half as great in the inner portion of the tuber as in the skin. There is, 

 nevertheless, a considerable amount of the furfurol-yielding compounds 

 in the fleshy part of the potato. Inasmuch as the fungus has practically 

 no effect on the skin, it is to be considered that practically all changes 

 in the pentosan content that take place during rotting are in the inner 

 portion of the tuber. The results obtained from the pentosan determina- 

 tions on the sound and the rotted portions of the potato tubers are shown 

 in Table XII. 



Table XII. — Pentosan and tnethyl-pentosan content of sound and rotted quarters of 



potatoes 



[Expressed as percentage of pentosans, wet weight] 



Infected with F. oxysporum 



29 



30 



35 



40 



Infected with F. radicicola: 



171 



174 



176 



Sound quarter. 



Total 

 pento- 

 sans. 



53 

 53 

 45 

 52 



28 

 37 

 25 



Pen- 

 tosans. 



0.47 

 .41 

 •36 

 .42 



32 

 19 



Methyl 



pen- 

 tosans. 



O. 06 



. 12 

 .09 

 . 10 



•05 

 •05 

 .06 



Rotted quarter. 



Total 

 pento- 

 sans. 



o. 50 



.46 

 •44 

 •37 



•25 

 .29 

 .26 



Pen- 

 tosans. 



0-35 



•35 

 •35 

 .26 



. 20 

 . 24 



Methyl 



pen- 

 tosans. 



0.15 

 . II 

 .09 

 . II 



•05 

 •05 

 •05 



