ORIGIN AND NATURE OF THE MUCILAGE IN THE CACTI 1 65 
colloidal properties are thus quite altered, and the complex takes on the 
character of a suspension (Lloyd, 1918^). By means of alcohol, further 
dehydration followed by precipitation occurs and the amount of adsorbed 
stain is reduced, when the mucilage may be recovered as such but with 
slightly altered physical properties, since it no longer swells indefinitely in 
water. The following stains have been investigated as to this behavior. 
They are mentioned in series, beginning with the most vigorously adsorbed 
and therefore the most active in reducing viscosity. The material was 
from Opuntia Blakeana. Ruthenium red > neutral red > Bismarck brown 
= gentian violet = methylene blue > safranin > methyl green > eryth- 
rosin. The viscosity was unaltered after nine days by fuchsin, methyl 
blue, coralline, orange G, methyl orange. For the concentrations used, an 
observable lowering of viscosity followed after twenty-four to forty-eight 
hours in the case of the most vigorously adsorbed stains. A brief examina- 
tion of the mucilage of Ulmus fidva and of Linum (seed-coat) has indicated 
that they behave similarly toward ruthenium red and neutral red. Further 
investigation is in progress. 
Conclusions 
1. Mucilage in the cacti, mallows, and tragacanth arises within special- 
ized parenchyma cells by hydrolysis of the cellulose wall, which is not secon- 
darily thickened. The first visibly demonstrable change is from cellulose to 
a hydrocellulose ; from this the mucilage arises. As this hydrates, it swells 
and compresses the protoplasm toward the middle of the cell. The proto- 
plasm remains attached more or less to the pits (where little or no hydrolysis 
of the wall appears to occur), giving rise to radiating strands mimicking the 
strands within the protoplast extending from the nucleus to the wall-layer. 
The mucilage shows lamination which is determined by water content. 
It is quite possibly predetermined by the apposed layers of cellulose in the 
original cell wall. The lamination has evidently led certain previous ob- 
servers to the idea that the mucilage arises as a secondary thickening in the 
structural sense. 
The mucilage is neither laid down as a secondary layer, nor is it secreted 
within the protoplast, nor yet is it a secretion thrown out as mucilage from 
the outer surface of the protoplasm. 
In tragacanth it appears that the hydrolysis of the cell walls is more 
extensive than in such forms as Opuntia, Tilia, the mallows, and is at the 
same time accompanied by digestion of the middle lamella. 
2. The mucilage adsorbs certain dyes with great vigor, others with 
lesser and different degrees of vigor, and still others not at all. 
The viscosity of the mucilage is lowered by those dyes which are ad- 
sorbed, at a rate and to an extent in direct relation to the degree of ad- 
sorption. 
See summary in Tunmann (1913). 
