24 THE ROYAL SOCIETY OF CANADA 



there was some success, but not by procedures in accordance with 

 the statements of the text books. What also emerged was the dis- 

 covery that certain stains, of which ruthenium red may be cited as an 

 example, caused flocculation of cactus mucilage, so that, in the course 

 of time, its viscidity entirely disappeared.^ It was further determined 

 that those dyes which are adsorbed by the mucilage have this effect in 

 common, while those which are not absorbed do not in the least affect 

 the viscidity; and, finally, that the vigour with which the viscidity 

 is lowered is directly related to the degree of adsorption. 



These facts, in a general sense, were determined by a series of 

 experiments leading to and culminating in the following. Small 

 cubes of tissue were cut from fresh joints of Opuntia Blakeana. These 

 were allowed to lie in water for some hours till each was surrounded 

 by a drop of clear, dense mucilage derived by the hydration of the 

 mucilage of such cells as broke out under the swelling of the contained 

 matter.^ At this point the mucilage is very viscid, so that, upon 

 lifting a bit of tissue out of the water a long rope hangs therefrom, but 

 does not break. The tenacity of this rope is constant for a long period 

 of days, but the effect of any reagent which affects its viscidity be- 

 comes apparent in its lessened diameter, in its beading, or in its entire 

 loss of tenacity. A measure, albeit somewhat rough, was thus had of 

 alterations in viscidity. 



Into each of a series of small glass vessels a single cube of tissue 

 with its adherent mucilage was placed, and sufficient solution of dye of 

 moderate concentration added to surround but not to cover the blob 

 of mucilage. If the dye was adsorbed, this fact became apparent in 

 the deeper colour of the mucilage as compared with that of the sur- 

 rounding fluid. If not, after diffusion was complete the mucilage was 

 indistinguishable as to colour. After some time the cellulose walls of 

 the tissue also adsorbed the stain or not, and the fact could be readily 

 determined by inspection. Such stains as wcx'e available at the 

 Coastal Laboratory of the Carnegie Institution of Washington were 

 tried. The experiment ran for ten days, during which period day-to- 



* After the viscidity of the mixture has disappeared, the emulsoid may be pre- 

 cipitated by alcohol, when it is found to have become a jelly showing limited swelling 

 in water, (ruthenium red; neutral red.) It should be added that when the density 

 of the mucilage is high enough (as in an unopened mucilage cell) the colour is ad- 

 sorbed without flocculation. I have observed analogous behaviour in tannin cells 

 (Tannin-Colloid complexes in the fruit of the Persimmon. Biochem. Bull. 1 : 7-41. 

 S. 1911.) 



"Lloyd, F. E. Origin and Nature of the Mucilage in Cacti. Am. Jour. Bot. 6: 

 166. April, 1919. 



