6 
BULLETIN 56, HAWAII EXPERIMENT STATION 
the older members of the group including developing stems with more 
than one leaf, and (b) plants with stem undeveloped, composed 
chiefly of "spike" rootstocks. 
LABORATORY METHODS 
Determination was made of the reducing and nonreducing sugars 
in the sap of the plant. Immediately after the plant was dug the 
parts to be analyzed 
were ground in a meat 
chopper and the juice 
was expressed, when 
necessary, by means of 
a screw press. 2 Usually 
the tough fibers of the 
plant clogged the meat 
chopper and produced 
a combined grinding 
and pressing effect. 
The resulting pulp was 
very dry and the ex- 
pressed sap could be 
drawn off at the oppo_ 
site end of the grinder 
thus omitting the use 
of the press. Twenty- 
five cubic centimeters 
of the sap was immedi- 
ately pipetted out for 
determination of reduc- 
ing and nonreducing 
sugars. Clarification 
of the sap by means of 
neutral lead acetate so- 
lution was not always 
successf ul . Certain 
plant substances, prob- 
ably some of the gums, 
which failed to be pre- 
cipitated by the lead 
acetate solution, were 
subsequently thrown 
down by the Fehlingso- 
ution, during the determination of reducing sugars as a flocculent 
precipitate. 
To eliminate this difficulty the following procedure was followed: 
Fifty cubic centimeters of 95 per cent ethyl alcohol was poured into 
25 cubic centimeters of the freshly expressed sap stirred continuously. 
This produced a flocculent precipitate which was easily filtered out. 
Fifty cubic centimeters of the filtrate was pipetted 3 into a beaker 
' This method is subject to criticism when the leaves are used because they contain invertase which 
may cause rapid inversion of the sucrose. This trouble is reduced to a minimum, however, when only 
stems and roots are used because of their very low invertase content. Evidently very little inversion 
took place since the hexose content in all the leaf samples was very low. (See Table 6.) 
Shrinkage of volume, of course, occurs upon the addition o e alcohol to sap, which fact is taken into 
account when the percentage of sugars is computed. 
Fig. 5. — Four generations of rootstocks. Note the progressive 
change in shape and tendency of the rootstocks to grow out of 
the ground. Secondary growth is appearing on the first-genera- 
tion rootstock 
