210 Ingvar Jorgensen and XValter Stiles. 
7. Preparation of Material. 
In order to obtain correct results in the estimation of substances 
so liable to change by enzyme action as carbohydrates, special care 
has to be taken to avoid such change in the preparation of the 
material for analysis. 
Brown and Morris (1893) therefore dried the leaves rapidly at 
from 75 n C to 80 n C before estimating starch, and for estimating 
sugars the leaves were dried on wire-bottomed trays in a steam 
oven. Parkin (1911) used a similar method. The leaves were air 
dried at a temperature sufficiently low to prevent discoloration. In 
both cases the dried leaves were then powdered. That the sugars 
are extracted unchanged by this method was shown by Parkin by 
estimating them in material so prepared, and in leaves killed by 
immersion in liquid air which were subsequently ground up while 
frozen and then thrown into boiling water (containing a few drops 
of ammonia to neutralise any acid from the leaf) in order to kill the 
enzymes. 
The following table shows that the two methods give almost 
identical results. 
The numbers for two separate examples (I and II) are given. 
Table XXIX. 
Comparison of Sugars in A ir-dried Leaf and in Leaf 
treated with Liquid Air. 
— 
Leaf treated with 
liquid air. 
Air-dried Leaf. 
I 
II 
I 
II 
Sucrose 
12-84 
1046 
12-74 
10-42 
Reducing Sugars ... 
5-94 
12-87 
5-67 
12-38 
Total Sugar ... 
18-78 
23-33 
18-41 
22-8 
Sucrose 
Hexose 
1 : 0-46 
1 : 1-23 
1 : 0-45 
1 : 1-19 
From the leaf powder of Tropceolnm Brown and Morris 
extracted fat and chlorophyll with ether. The residue was then 
twice extracted for 24 hours with 80% alcohol at 40°C. The 
alcoholic extract was used for the estimation of sugars, the residue 
contained the starch. 
In the case of the Snowdrop where the leaf contains no starch, 
Parkin extracted the sugars by four extractions with cold water 
