THE CARBOHYDRATES OF THE CACTI. 45 



variety of ways, that this is not confined to the metamorphosis of the cell 

 wall or middle lamella, and is often formed in the interior of the cell. The 

 mucilages are undoubtedly used for a variety of purposes by the plant. The 

 interest here is confined to their use as food material and their property 

 of water imbibition. 



In order to obtain the mucilage in as pure a condition as possible for 

 further study, various procedures may be followed. A crude product can 

 be obtained easily by first cutting up the plant material with a meat chopper 

 and slowly pressing the mass through a muslin cloth. The portion which 

 passes through is a thick, clear fluid. However, this latter material always 

 contains reducing sugars and a little starch. 



When the cactus joints are placed under a bell-jar in an atmosphere con- 

 taining ether, chloroform, or acetone, after about 24 hours the heavy 

 mucilage exudes from the cut surfaces of the joint. After several days a 

 considerable quantity can thus be collected. 



The most satisfactory results were obtained by cutting the cactus into 

 pieces of about 1 c. c. These were placed in a quantity of distilled water 

 equal to the volume of the pieces, and a few drops of formaldehyde were 

 added. After 12 hours the mixture was poured onto a cheese-cloth filter 

 and the liquid was allowed to drain off. The pieces of cactus were again 

 placed in an equal quantity of fresh distilled water and after 12 hours the 

 mass was again filtered. In order to free from small particles of tissue, the 

 filtrate was passed through a very fine chiffon. The resulting filtrate was 

 clear, colorless, and of about the consistency of fresh egg albumin. It had 

 a decided acid reaction and, on heating, it browned and became thin, 

 probably on account of hydrolysis. To the solution of the mucilage was 

 added 3 times the volume of 95 per cent alcohol. This caused a white, 

 gelatinous precipitate, which was rapidly filtered and washed. The amor- 

 phous, elastic mass was dried in vacuum over calcium chloride. Allowed 

 to remain in the air, it became gray and finally dark brown. It dissolved 

 in water to a mucilage with a small quantity of insoluble matter, probably 

 coagulated proteins. The whole original precipitate was, therefore, again 

 dissolved in water, filtered from the small amount of insoluble matter, 

 precipitated again with alcohol, filtered, and dried in the same way. This 

 material dissolved to a clear thick mucilage in water. 



The solution exhibited still a slightly acid reaction. It showed a decided 

 dextro-rotatory power, although the value was not constant in all prepara- 

 tions. It was impossible to salt out the mucilage from solution with 

 ammonium sulphate or lead acetate. The free mucilage gave no definite 

 coloration with iodine or with chlorzinc iodine. The solution did not show 

 the slightest reduction of Fehling's solution. It was, however, very easily 

 hydrolyzed; after heating about 10 minutes with 0.5 per cent hydrochloric 

 acid, the mixture reduced Fehling's solution very rapidly. A preparation 

 of invertase (made as described above) was, however, absolutely without 

 any effect after 48 hours, nor was the solution affected by pure baker's yeast. 



