B.—CHEMISTRY 41 
are of absorbing interest and are under close investigation. ‘These 
glycogen specimens have chain lengths of 12 and 18 glucose units, but 
they display little or no tendency towards molecular aggregation. It 
may possibly be promoted by the interlocking of adjacent chains by forces 
corresponding to those which bring about co-ordination, and by the so- 
called extraneous materials such as combined phosphate or silica, 
What seems clear is that starch polysaccharides of comparatively short 
chain-lengths of ro or so glucose units are devoid of this property. 
The occurrence of cellulose and starch in the green leaf of the growing 
plant has long been recognised, and so also has the occurrence of a very 
different polysaccharide inulin in the root organ of the Composite and 
related families, where it replaces the starch found in other types of plant. 
The recent discovery of the presence of a water soluble polysaccharide in 
the leaf of certain grasses has shed new light on the réle of fructose and 
its synthetic operations in the plant. This polysaccharide is a levan 
and is composed of repeating units of fructofuranose united through the 
positions 2 and 6, thus displaying a different mode of combination of its 
fructose members from that which obtains in inulin. The formula of 
this levan is given below and its chain length is almost certainly that of 
ro such members of fructofuranose : 
Very different, although related to this, is the type of combination which 
characterises the mode of union of successive fructofuranose members 
comprised in inulin. The break-down of inulin is easily accomplished 
with the mildest acid reagents, giving rise to and indeed providing the best 
source of fructose. What has not been recognised until recently is that 
inulin may under the most unforeseen circumstances also give rise to a 
biose anhydride. An analogy may therefore be drawn between the break- 
down of this carbohydrate to a biose derivative and the break-down of 
starch and glycogen to maltose and that of cellulose to cellobiose. So 
sensitive is inulin in this respect that some of the dextro-rotatory products 
given in the literature as substituted inulins are really to be formulated 
as the 1 : 2-difructofuranose anhydride : 
HOCH, ig fag 
H HO SG Po NGA 
H 0 ——cHs CH;0H 
oH H on 4 
H 
