206 Ingvar Jorgensen and Walter Stiles. 
only sugars they found were sucrose, glucose, fructose and maltose. 
Pentoses were tested for, but not found. It is to be regretted that 
Brown and Morris do not state definitely what tests they applied for 
the various sugars, as their results have been accepted without ques- 
ion by most later workers. The presence of cane sugar seems quite 
definitely established, as leaf extracts after treatment with invertase 
increase in reducing power and change in optical activity, and this 
change is not very different from that which would result if the increase 
in reducing power were due to the inversion of cane sugar into glucose 
and fructose. They were also able to show the presence of maltose 
by obtaining maltose phenyl-osazone from leaf extracts. Similarly 
glucose phenyl-osazone is produced, but no evidence is given as to 
why it is concluded that ^-glucose and rf-fructose are the only 
hexoses present, beyond the fact that they could obtain no other 
phenyl-osazones. It should be noted that rf-mannose gives the 
same osazone as rf-glucose and rf-fructose, while the l forms of these 
three hexoses which are always stated to be absent from the leaf, 
give a phenyl-osazone of the same crystalline form and the same 
melting point as the d forms of the sugars (see e.g., Tollens, 1914). 
More recent work, however, has never succeeded in revealing the 
presence of any hexoses other than ^-fructose and rf-glucose, though 
on the other hand it must be admitted that no definite evidence 
has so far been brought forward in favour of the absence of all 
other hexoses. For example, Parkin (1911) was unable to obtain 
any osazone from extracts of snowdrop leaves other than glucose 
phenyl-osazone, and hence concludes that galactose and mannose 
are both absent. This argument is satisfactory for galactose, but 
it does not hold for mannose, as that sugar gives the same osazone 
as glucose and fructose. 
Moreover, the recent work of Davis, Daish and Sawyer (1916) 
has cast grave doubt on the presence of maltose in leaves, which 
they find only present in estimable quantity as a result of enzyme 
action in leaves not instantaneously killed. Contrary too, to Brown 
and Morris, these last workers conclude that free pentoses are 
present in leaves. 
They base this conclusion (Davis and Sawyer, 1914) on the 
fact that leaf extracts contain substances soluble in 80% alcohol 
which are not precipitated by basic lead acetate, which are 
unfermentable by ordinary yeasts and which exercise a cupric- 
reducing power after other sugars have been fermented away. 
There are of course many sugars which would fulfil these conditions, 
