124 THE CARBOHYDRATES 



phloroglucinol and hydrochloric acid a bright red coloration 

 results. 



MUCILAGE. 



The term mucilage is applied to those substances which 

 with water produce a slimy liquid. Mucilage is widely dis- 

 tributed, and occurs in all or nearly all classes of plants. 

 Mucilage-secreting hairs, or comparable structures, occur in 

 various Muscineae, Filices, and especially in the Phanerogams ; 

 mucilage sacs or canals are found in certain Muscineae, e.g., 

 Anthoceros, Marattiaceae, some Cycadaceae, and Phanerogams ; 

 finally, the external walls of plants may be generally mucila- 

 ginous ; e.g., in very many Algaj, the hibernaculae of some 

 aquatic Phanerogams, like Utricularia and Myriophyllinn, and 

 finally in the coats of seeds and fruits, such as Lepidium and 

 Sterculia scaphigeva respectively, in which cases the superficial 

 cell walls are mucilaginous. Mucilage is not infrequently 

 associated with other substances ; thus in the case of mucilage- 

 secreting hairs, it is sometimes associated with tannin, and in 

 many plants, especially in the mucilage sacs of many Mono- 

 cotyledons, calcium oxalate is found. 



The constitution of mucilages is as yet unknown ; they 

 are, however, related pretty closely both to cellulose and to 

 arabin. In fact, by some authors they are regarded as de- 

 composition products of cellulose, produced either by over- 

 nutrition of certain cells or by bacterial action ; * according to 

 Wiesner, all gums are produced by a diastatic ferment acting 

 on cellulose ; although it is not possible to express any definite 

 views on the subject, it would appear not improbable that in 

 many cases the formation of gums and gum-like substances in 

 the plant is a morbid condition. Mohl was able to show in 

 the case of tragacanth gum that this substance was produced 

 by the metamorphosis of the cells of the medullary rays. 



That mucilages are not all of the same constitution is 

 shown by the fact that the mucilaginous substance obtained 

 from Fucus (caragheen mucilage) on hydrolysis with dilute 

 sulphuric acid yields galactose, while salep mucilage, obtained 

 from Orchis Mario, on a similar treatment yields mannose. 



* See Greig Smith ; " J. Soc. Chein. Ind.," 1904, 105, 972. 



