196 THE CONSTITUENTS OF PLANTS. IX. 



by the action of diastase upon starch, dextrin being simul- 

 taneously produced. Maltose is a crystalline substance which 

 undergoes fermentation under the influence of yeast, being 

 first converted by an enzyme present in the yeast into glucose. 

 It reduces copper solutions and in most of its properties closely 

 resembles glucose. It is probably the form in which starch 

 and other carbohydrates undergo translocation in plants. 



The other saccharobioses are less important. 



Mycose, Trehalose, C^H^O U + ^H Z O, have been found in 

 several fungi and in ergot of rye. 



Agavose, C^H^On, has been found in a Mexican plant 

 Agave Americana, from the juice of which a fermented drink 

 called pulque is made. The sugar is inactive and reduces 

 copper salts. * 



Lupeose, C^H^On. According to Schulzej lupine seeds 

 contain a sugar of the above composition. It yields galactose 

 and fructose by hydrolysis. 



(c) Trisaccharides, Saccharotrioses, Hexo-trioses. 



Meletriose, Rafflnose, or Melitose, C 1H H 82 O lr ,, occurs in 

 Australian manna (Eucalyptus), in cotton seeds, and in small 

 quantities in the juice of sugar beets, and accumulates in the 

 molasses from which it can be prepared. 



It crystallizes in needles or prisms containing three mole- 

 cules of water. It is very soluble and does not reduce copper 

 salts. It is fermentable. 



The Pentoses, C 5 H 10 5 . 



These substances must now be included in the carbohydrates 

 and are of considerable importance because of the common 

 occurrence in plants of substances which readily yield them. 



The most important pentoses are 



Arabinose, d-, 1-, and inactive 



Xylose 



Eibose 



* Michaud and Tristan, Araer. Chem. Journal 14 (1893), 548. 

 t Ber. 25, 2213 ; Jour. Chem. Soc. 1892, abst. 1171. 



