Translocation of Latex and the Multiple Razor. 19 J 
limits the thickness of tissue which can be cut as, when mounted, 
it extends only §" beyond the top of the block. 
Being easily and inexpensively made the instrument should 
prove of some use in botanical laboratories wherever translocation 
experiments are carried out either in teaching or in research. 
Two species of Lactuca have been examined for latex trans¬ 
location. Faivre (1) used seedlings grown in darkness and Kniep (4) 
criticises the relevancy of his results because the laticiferous vessels 
may grow in darkness while there is no increase in the latex, which 
therefore becomes diluted with a watery fluid. This objection was 
avoided by growing the plants in the open ill flower-pots until at 
least six well-developed leaves were present. Lactuca virosa , L. 
was examined first. The potted plant was taken from the garden ; 
one leaf was arranged carefully and without injury along a block of 
wood and ‘guillotined’ with the multiple razor, which cut the leaf 
into four parts, each half an inch long, the severance of the parts 
taking place at exactly the same time as the dividing of the leaf 
from the plant. The latex in each part should, therefore, have been 
in the same condition as it was in the uncut leaf; at least, there 
should have been the same amount of latex in each portion as 
there was before any cutting took place. 
A series of thick longitudinal sections of the midrib then 
showed the latex to be dense and abundant in each part of the leaf. 
No gradation in density could be traced in the different parts of 
the leaf (Fig. 4, a-d). 
The plant was then placed in darkness for 48 hours and a leaf 
similar to the first one was treated in the same way. The longi¬ 
tudinal sections here showed a marked difference ; not only was 
the latex less dense and less abundant even in the basal part of 
the leaf, i.e., the part next the stem, but the portions showed a 
successive decrease in the density of the latex from base to apex 
(Fig. 5, a-d). 
The experiment was carried further and in four days a third 
leaf was found to have very little latex, so little indeed, that it was 
difficult to distinguish whether there was any gradation (Fig. 6, a-d). 
Lactuca scariola, L. was also examined and yielded similar results. 
This gradation within the leaf has been found in the sugars of 
the sieve-tubes by Mangham (5) in his work on translocation of 
carbohydrates and emphasises in the matter of translocation the 
affinity between latex and assimilable reserves already pointed out 
