18 VEGETABLE PHYSIOLOGY. LESSON 6. 



From the bark of these trees it exudes as a thick juice, which subse- 

 quently concretes into tears. 



99. Gum arabic is combined with cerasine, in the gum of the 

 cherry and plum. 



100. Mucilage is found in many of the mallow tribe, as marsh 

 mallow, and in linseed. 



101. CERASINE is that part of the gum of the cherry (cerasus), 

 plum, and almond trees which is insoluble in cold water. 



102. PECTINB is a substance procured from pulpy fruits, as the 

 pear and apple ; it forms a jelly with water, and when dried resem- 

 bles gum, or isinglass. 



103. SUGAR is a substance which exists in many plants : they have 

 been divided into those which undergo vinous fermentation, as cane, 

 and grape sugar, and those which are not fermentesible, as mannite. 



104. Cane sugar comes from the sugar-cane (Saccharum officina- 

 rum), beet-root (Beta vulgaris), sugar-maple (Acer saccharinum) , 

 Chinese sugar-cane (Sorghum sativum), and many other plants. 



105. MANNITE is the chief ingredient of manna, which exudes 

 from the Ornus europcBa and Ornus rotundifolia ; it is exported from 

 Sicily and Calabria, under the name of flake manna. It is also 

 found in mushrooms, celery, and many species of sea- weeds. 



LESSON VI. 



OILS, WAX, CHLOEOPHYLLE, RESINOUS PRODUCTS, CAOUTCHOUC. 



106. Oil abounds to a great extent in the vegetable kingdom, 

 and cells appear to be formed for its special reception ; it seems to 

 hold the same relation to the vegetable that fat holds to the animal 

 kingdom. 



107. This substance is chiefly met with in the seeds of plants ; it 

 is highly nutritious (to the plant), and appears to nourish the em- 

 bryo, until organs are developed capable of obtaining sustenance from 

 other sources. 



108. The oils found in plants are either fixed or essential. The 

 former are found (drying oil) in linseed ; fat oils from the olive 

 (Olea europcea), and solid, as lard, in the palm. 



109. The fat oils contain a large quantity of stearine, and are 

 hence used as a substitute for animal fat in the composition of can- 



