Feb. 34,1933 
Distribution of Pentosans in the Corn Plant 
661 
Table IV .—Free pentoses in the corn plant at various stages of growth 
Series 
No. 
Stage of growth. 
Part of plant. 
Pentoses. 
4 
3 feet. 
Tops. 
Gm. 
0. 067 
. 062 
Per cent. 
73 
.69 
fin 
5 
Tassel 
/Leaves. 
[Stalks. 
.065 
. 04.7 
[Leaves. 
. 09 
• 52 
1. 66 
.87 
•39 
.92 
•35 
•25 
•47 
.76 
•25 
. 18 
.26 
6 
Silk forming. 
< Stalks. 
T CA 
Husks. 
• I54 
. O78 
.036 
.086 
[Leaves. 
7 
Milk 
Stalks. 
Husks. 
Cobs. 
• 
. 024 . 
(Leaves. 
. 044 
Stalks. 
. 072 
8 
Dent. 
Husks.. 
Com. 
. 017 
Cobs. 
. 025 
In an earlier paper (jo) pentoses to the extent of 0.6 per cent were 
reported in the stalk and cob of every green com which was analyzed 
according to the method of Davis and Sawyer (4). A decrease of 6 mgm. 
could therefore be accounted for by a destruction of the free pentoses of 
the com stover. In addition 5 mgm. must be deducted for the difference 
in the duplicate weights of phloroglucid. A loss of 11 to 12 mgm., or 5 
per cent, of pentosans must therefore be attributed to these two factors. 
A destruction of more than 5 per cent, on the other hand, may safely be 
attributed to the destruction of the pentosans themselves. 
FREE PENTOSES 
Ten grams of the material were placed in an Erlenmeyer flask, to¬ 
gether with approximately 5 gm. of calcium carbonate to neutralize the 
acidity and 100 to 150 cc. of 85 per cent alcohol. The samples were 
placed in a boiling water bath and refluxed. Two extractions of three 
to four hours were made. The insoluble material was filtered away and 
the alcohol evaporated. The residue was taken up with water, filtered, 
and finally distilled as usual with 12 per cent hydrochloric acid. The 
results are given in Table IV. 
No extractions were made upon the plant material of the early stages 
because of the lack of material. It will be noted that the percentage of 
free pentoses is approximately the same in the leaves and stalks of series 
4 and 6. The outstanding feature of Table IV is the high percentage of 
free pentoses in the stalks of the plants of the sixth series. Shaw and 
Wright (16) have published a table in which the amount of reducing 
sugar in the com plant at the different stages of growth is given. At the 
stage at which the kernels are forming, which corresponds to series 6 in 
Table IV, they find the largest amount of reducing sugar, namely, 20.3 
per cent. Coincidently, the highest percentage of free pentoses was 
found in the stalks at this stage of growth. 
Further evidence that free pentoses are contained in com tissue was 
obtained by fermenting the alcohol-extracted sugars with yeast. The 
extracted sugars were made up with suitable nutrients and inoculated 
with a pure culture of yeast. Vigorous evolution of carbon dioxid ensued 
for a few days, but soon ceased. After 15 days the fermented liquid was 
analyzed for reducing sugars. From 500 gm. of com tissue 3.54 gm. of 
sugar calculated as xylose remained unfermented by the yeast. 
