92 BOTANICAL MICROTECHNIQUE. 



being dissolved by concentrated sulphuric acidw\t\\ a yellow- 

 ish or reddish brown color. It differs from fungus-gamboge 

 in taking no olive-brown color with ferric chloride. 



5. Retinic Acid from Lenzites sepiaria. 



149. According to Bachmann (II, 7), opaque globules or 

 granules of a retinic acid are found on the membranes of 

 Lenzites sepiaria in many places. These are quickly dissolved 

 by a watery or alcoholic solution of caustic potash or soda 

 with a dark olive-green color. 



6. Glucosides. 



150. The name glucosides is given to a group of sub- 

 stances resembling compound ethers, widely distributed in 

 trie vegetable kingdom, which are characterized by being 

 decomposed by various reagents, especially acids, alkalies, 

 or ferments, into a species of sugar and one or several other 

 compounds. Usually this species of sugar is glucose. But 

 there are commonly included in the glucosides compounds 

 which do not yield a true sugar, like, e.g., phloretin, which 

 forms phloroglucin instead of glucose (cf. Beilstein, III, 322.) 



The glucosides which yield glucose on decomposition 

 may be microchemically recognized by the aid of Fehling's 

 solution (cf. 119) under some circumstances, even when 

 they do not directly reduce a copper solution, but only after 

 the glucose has been separated from them, as by warming 

 "with dilute sulphuric acid. There are also many glucosides 

 which directly reduce Fehling's solution. 



In their other relations the glucosides show great differ- 

 ences, and no reactions common to the entire group are yet 

 known. We must therefore confine ourselves here to the 

 special description of some glucosides for which special reac- 

 tions, microchemically applicable, have been suggested. 



a. Coniferin, C 16 H 22 O 8 . 



151. Coniferin has been macrochemically produced from 

 the cambial juices of various Coniferce. But, although 



