HISTORICAL. 25 



of course, the chemical nature of the carbohydrates in the organism under 

 investigation. 



For the succulent plants especially very little data of this nature have 

 been gathered. In 1902 Harlay 1 published some investigations on the 

 mucilage of Opuntia vulgaris. The mucilaginous substances are located in 

 special, large cells. These were made visible in material which was con- 

 served in alcohol and examined with lead subacetate. By allowing the 

 cactus joints to remain in an atmosphere of ether, Harlay found that the 

 mucilages exuded as a clear, slightly colored, thick liquid. He obtained the 

 mucilage by removing the exterior chlorophyllous portion, chopping, grind- 

 ing with sharp sand, heating with water at 110, filtering through cloth, 

 and precipitating with 90 per cent alcohol; this precipitate was filtered off, 

 washed with alcohol and dried. Thus he obtained a gray powder, which 

 when dissolved in water did not reduce Fehling's solution, but always con- 

 tained a small amount of inorganic material. The aqueous solution could 

 not be filtered. His analysis indicated the presence of galactose and 

 arabinose. 



Recently Long 2 made some analyses of the carbohydrate-content of 

 Echinocactus in collaboration with the studies of MacDougal on the water 

 balance and desiccation of this plant. 



1 HARLAY, V. Sur le mucilage du cactus a raquettes, Opuntia vulgaris Mil. Jour, de 



Pharm. et de Chem. (6), 16, 193-198, 1902. 

 'MACDOUGAL, D. T., E. R. LONG, and J. G. BBOWN. End results of desiccation and 



respiration in succulent plants. Physiol. Researches 1, 289-325, 1915. 

 LONG, E. R. Further results in desiccation and respiration of Echinocactus. Bot. 



Gaz., 65, 334-358, 1918. 



