VEGETABLE CYTOLOGY 9 I 



Mucilage is stored as reserve food in the tubers of Salep and 

 many other Orchids and also in the seeds of some species .of the 

 Leguminosae. 



Cell-content mucilage has been found in the leaves of Alos, 

 the rhizomes of Triticum, the bulb scales of Squill and Onion and 

 in certain cells of many other Monocotyledons, especially those 

 containing rap hides. 



Membrane mucilage has been observed in Barosma, Ulmus, 

 Althaa, Linum, Astragalus, and Acacia species, in the Blue-green 

 Algae, and many of the Brown and Red Algae. 



When mucilage is collected in the form of an exudate from shrubs 

 and trees it constitutes what is termed a gum. Many of these gums 

 are used in pharmacy, medicine and the arts. The three most im- 

 portant from a pharmaceutical standpoint are: Acacia, yielded by 

 Acacia Senegal and other species of Acacia; Tragacanth, yielded by 

 Astragalus gummifer and other Asiatic species of Astragalus; and 

 Cherry Gum, obtained from Prunus Cerasus and its varieties. 



Mucilage may be demonstrated in plant tissues containing it by 

 placing sections of these in a deep blue solution of methylene-blue 

 in equal parts of alcohol, glycerin and water on a glass slide, allowing 

 them to remain in the solution for several minutes, then draining 

 off the stain and mounting in glycerin. Those cells containing muci- 

 lage will exhibit bluish contents. 



21. Fixed Oils and Fats. These are fatty acid-esters of glycerin 

 which are found in the vacuoles of cells or formed with the cell 

 walls from which they may be liberated as globules upon treating 

 sections with chloral hydrate or sulphuric acid or heating them. 

 They are quite soluble in ether, chloroform, benzol, acetone and 

 volatile oils but insoluble in water, and, with the exception of castor 

 oil, insoluble in alcohol. They are readily distinguished from the 

 volatile oils in that they leave a greasy stain upon paper which does 

 not disappear. Fixed oils and fats take a brownish to black color 

 with osmic acid, a red color with alkannin or Sudan III and a blue 

 color with cyanin. In Vaucheria, the Diatoms and a few of the 

 other Thallophytes, fixed oil is formed in the chromatophores in- 

 stead of starch as the first visible product of photosynthesis. In 

 higher plants it is generally found in storage regions, such as the 



