26 MICRO-CHEMICAL REAGENTS. 



evaporation. When this expedient does not pro- 

 duce the desired effect, recourse should be had to 

 the air-pump. 



Alcohol is a solvent for volatile oils and resins, 

 while fatty oils and vegetable wax are insoluble in 

 cold alcohol, though it causes the oil globules to 

 become confluent. 



In tissues, e. g. nectaries, which contain much 

 cane sugar, this may be forced by the use of abso- 

 lute alcohol to separate in small stellate crystals 

 soluble in water. 1 



In all tissues containing inulin the prolonged 

 action of alcohol effects its precipitation within 

 the cell in the form of sphaero-crystals ; e. g. in 

 Inula, Helianthus, Dahlia, etc. Other sphaero- 

 crystal-forming substances, such as hesperidin, 2 

 crystallize under the same treatment. (See Inulin 

 and Hesperidin.) 



Asparagin may also be detected by the use of 

 absolute alcohol, the sections that are tested being 

 alternately moistened with the reagent and allowed 

 to dry, when the asparagin 3 crystallizes out often 

 with other substances. It is recognized by its in- 



1 Bonnier : Les Nectaires. Ann. Sc. Nat., 1879, T. 8, pi. 8, figs. 124, 126. 



2 Prantl : Das Inulin, 1870. Rosenvinge: Sfaerokrystaller hos Mesem- 

 brianthemum. Nat. Foren. vidsk. Meddelelser, 1877-78, p. 305, with 

 table (with literature of the subject). Pfeffer: Sachs' Lehrbuch, 1874, p. 

 65. Russow: Leitbiindelkryptogamen, 1872, p. no. 



3 Hartig: Entwickelung des Pflanzenkeimes, 1858. Pfeffer: Ann. Sci. 

 Nat., Bot., 5 Ser., T. XIX., p. 391. Sachs: Lehrbuch der Botanik, 1874, 

 p. 689. Borodin: Bot. Zeitung, 1878, p. 803. Detmer: Vergl. Physiol. d. 

 Keimungsprocesses, 1880, p. 171. 



