SPECIAL METHODS. 157 



scribed and by the fact that its hydrolytic splitting with 

 sulphuric acid yields no seminose, but most probably glu- 

 cose (cf. Reiss I, 761). 



[Winterstein's (I) recent researches give results which 

 differ in several respects from those of Reiss. He finds 

 amyloid soluble in cupr ammonia after a day. From this 

 solution it is not precipitated by acids, but is thrown down 

 by alcohol. Its composition seems to correspond to the 

 formula C 17 H 30 O 15 , and it appears to belong to Tollens' group 

 of Saccharo-colloids, though it is not certain that it is a single 

 compound. In spite of its bluing with iodine, it cannot be 

 regarded as very nearly related to starch.] 



b. ^Vound-gum. 



277. The name wound-gum is commonly given to a 

 substance which, according to Temme's researches (I), is 

 very abundantly secreted in the vessels by the surround- 

 ing starch-cells, in natural and artificial wounds, and, like 

 tyloses, closes their cavities. This wound-gum agrees, ac- 

 cording to Temme, with many sorts of gums in that it 

 yields oxalic and mucic acid on oxidation with nitric acid. 

 But it differs essentially from all gums in not swelling in 

 water and in being insoluble even in caustic potash and sul- 

 phuric acid. As has been recognized by Temme, wound- 

 gum is stained deep red by pJiloroglucin and hydrochloric 

 .acid. Molisch showed later (IV, 290) that it behaves just 

 like lignified membranes with aniline sulphate, metadiamido- 

 benzol, orcin, and thymol ; and he believes that wound-gum 

 contains vanillin in solution (cf. 254). 



c. The Gelatinous Sheaths of the Conjugatae, 



278. In many Zygnemacece the whole surface of the cell- 

 filaments is surrounded by a colorless covering, a " gelatin- 

 ous sheath," while in the Desmidiacece the excretion of jelly 

 is often limited to distinct regions on the membrane (cf. 

 Klebs II, and Hauptfleisch I). 



Since the refractive index of these jelly-sheaths differs 

 but little from that of water, they can be well recognized, 



