70 BOTANY part i 



of the cytoplasm. No sharp distinction can, however, be drawn 

 between the sap cavity and vacuoles, and, moreover, a number of 

 such vacuoles may take the place of the sap cavity itself. The cell 

 sap usually gives an acid reaction, owing to the presence in it of 

 organic acids or their salts. The substances held in solution by the 

 cell sap are very various. The soluble carbohydrates, in particular 

 the sugars (cane sugar, the glucoses, and especially grape sugar), 

 frequently occur in the cell sap. The glucoses may be recognised by 

 their reducing properties. 



If preparations containing glucose be placed in a solution of copper sulpliate, 

 and, after being washed out, are transferred to a solution of caustic potash and 

 heated to boiling, they will give a brick-red j^recipitate of cuprous oxide. If cane 

 sugar or saccharose be present, this same treatment gives only a blue colour to the 

 cell sap. 



Carbohydrates are transported in a plant principally in the form 

 of glucose ; cane sugar, on the contrary, is stored up as a reserve 

 material, as for example in the sugar-beet, in the stems of sugar- 

 cane, and in other plants from which the sugar of economic use is 

 derived. 



Inulin, a carbohydrate in solution in cell sap, behaves in the same way in the 

 Compositae. Treated with alcohol, inulin is precipitated in the form of small granules, 

 which may be redissolved in hot water. When portions of jjlants containing much 

 inulin, such as the root tubers of Dahlia variabilis, are placed in alcohol or dilute 

 glycerine, the inulin crystallises out and forms sphaerites, spheroidal bodies com- 

 posed of radiating crystal needles ; these sphere-crystals often show distinct 

 stratification and are easily broken up into wedge-shaped portions. Amides such as 

 GLUTAMIN and ASPARAGIN are also generally present in the cell sap. There are 

 frequently found dissolved in the cell sap tannins, alkaloids, and glucosides, 

 such as coniferin, hesjieridin, amygdalin, solanin, aesculin, saponin, and also bitter 

 principles related to the glucosides. Organic acids (malic, acetic, and oxalic 

 acids) are also of frequent occurrence in the cell sap ; thus, malic acid is usually 

 present in the leaves of the succulents. For the most jiart, these organic acids 

 unite with bases, and the salts which are formed often crystallise. The Field 

 Sorrel {Rumcx) and Wood Sorrel {Oxalis) are rich in binoxalate of potassium. 

 Species of Salicornia and Salsola contain sodium oxalate. The cell sap always 

 contains dissolved inorganic salts, especially nitrates, sulphates, and phosphates. 

 The different vacuoles of the same protoplast may have distinct contents ; thus 

 one may contain tannin and another be free from it, or one may have coloured and 

 another colourless sap. 



The cell sap is often coloured, principally by the so-called ANTHO- 

 CYANIN, which Hans Molisch, at least in some eases, regards as being 

 a non-nitrogenous glucoside (*-") ; it is probably a composite substance. 

 It is blue in an alkaline, and red in an acid reacting cell sap, and, 

 under certain conditions, also dark red, violet, dark blue, and even 

 blackish-blue. Anthocyanin can be obtained from the supersaturated 

 cell sap of a number of deeply coloured parts of plants in a crystalline 



