PAMMEL OX THE SEED-COATS OF EUPHORBIA. 55 I 



The chemistry of mucilages and gums is a subject still open 

 for investigation, especially in regard to the transitional stages. 

 Behrens^^ has divided all vegetable mucilages into — I. Charac- 

 teristic Mucilage: I. a. Mucilage from cellulose, as in roots of 

 SynipJiytioii ; b. Mucilage from starch, as in orchid bulbs. — II. 

 Amyloid. — III. Lichenin. — IV. Gum Mucilage. 



Giraud^^ has grouped these substances in the following 

 manner : 



I. Ordinary varieties of gum ; arabin, bassorin, cerasin. 

 II. Pectose : gum tragacanth (adragantin.) 

 III. Plant mucilages in a more restricted sense. 



1. Insoluble in alkalies and dilute acids. (The cellulose of quince 



mucilage.) 



2. Insoluble in alkalies, and forming with acids glucose and a va- 



riety of dextrin. (Flax-seed and mucilage of Irish moss.) 



3. Soluble in hot concentrated alkalies, and converted by acids into 



dextrin and glucose. 



Mucilage, which is an isomer of cellulose and bears the for- 

 mula Cg Hj^g O5 orCj2H2o O jQ,in some cases is derived from the 

 walls of cells which originally consisted of cellulose, but are gra- 

 dually transformed by a process of degeneration into mucilage. 

 In some cases, at least, it seems to be derived from the starch 

 granules, which are very common in the cells of seeds just before 

 they are ripe, as in Plantago Psyllium^ Liiuim^ Pyrus vulga- 

 ris. &c.'^'^ In others both sources can be recognized. 



Behrens says : 



" In a general way it may be said that all mucilage gives a blue-violet 

 and sometimes a yellow color with iodine, and with oxalic-nitric acid ; 

 that the gums give no color with iodine, but are transformed into mucic 

 acid by nitric acid.'' 



Some are precipitated by normal acetate of lead, while others 

 are precipitated only by basic acetate. Some mucilages are colored 

 red by rosolic acid, which color is not readily removed by alcohol. 

 This is true especially where the mucilage does not result from 



38. Behrens, 1. c. 



39. Compt. rend, vol, Ixxx. p. 477. See Fluckiger und Tschirch,, Engl, translation, 

 p. 164. 



40. Behrens, I.e., p. 371. 



