i64 
FRANCIS E. LLOYD 
their distribution and behavior during sweUing safranin m alcoholic solution 
was found very good. Thick sections are first stained and are then allowed 
to hydrate under the microscope. The total enlargement of the mucilage 
cells, due to the swelling of the imprisoned mucilage, is shown in the strains 
on the walls of the neighboring cells. This affords a picture of what may 
occur in the growing plant when under altered conditions of acidity the 
volume of the mucilage cells is altered. 
Neutral red. If living sections are placed in a very weakly acidified 
solution (I used acetic acid) of low concentration of the stain, the mucilage 
in situ will slowly take up the stain. Pronounced results may not be ex- 
pected in less than twenty-four hours. The cell walls also stain, their color 
being a deeper red as compared with the rose pink of the mucilage, a dif- 
ference doubtless referable to the degrees of dispersion of the colloidal 
systems. The annulae of the vessels also stain pink. In a strong solution 
of the stain the strong coloration of walls and protoplasm and the deep 
staining of the mucilage itself make observation difficult. 
In a slightly alkaline (to neutral red) solution the mucilage is not stained, 
or at length very slightly, although the included protoplast becomes deeply 
stained. The cell sap (in living sections) becomes loaded with the stain. 
Ruthenium red is taken up vigorously by the mucilage, as also by the 
cell walls and protoplasm. The stain has a dehydrating effect ont he muci- 
lage, which, when in high enough concentration, is sufficient to prevent 
sweUing. 
The above mentioned behavior of mucilage toward neutral red in acid 
and alkaline solution, and the dehydrating effect of ruthenium red, coupled 
with other frequent observations of my own which need not be detailed, 
led me to inquire more particularly into the relation of the mucilage as an 
emulsion colloid to dyes in general. It may be recalled that I showed some 
time ago (191 1) that tannin is adsorbed by a cellulose-like body when co- 
agulated, and only weakly so when not coagulated. This appears as a 
parallel behavior to that of cactus and other mucilage toward neutral red. 
At all events it was evident that the adsorption of a stain by the mucilage 
is related to the degree of hydration, and on attempting to investigate this 
relation it was further determined that certain dyes themselves alter the 
dispersive relations of the mucilage. E. g., it was found that ruthenium 
red forms membranes on the surface of a mass of mucilage (Opuntia, Tilia, 
etc.) as tannin does on a hydrated albumin. On mixing dyes with mucilage 
it developed that certain of them gradually lower the liscosity of the mucilage 
till it approaches closely that of water, and that the dyes which are most 
effective are those which are most strongly adsorbed. The emulsion- 
It is rather usual {e. g., Ishikawa, 1918) to quote this reagent as staining the pectic 
substances, allowing the inference to be drawn that it is specific in this regard. This is, 
however, not in any sense true, as I have previously observed (1916, p. 219.) Further on 
this, however, beyond. 
