CELL SAP 17 



and scattered throughout the specimen. These crystals are 

 composed of calcium oxalate. Add a little hydrochloric acid 

 and they will dissolve without effervescence. 



(k) Similar crystals may be found in many other plants, 

 e.g. Indian turnip (Arisaema), evening primrose (Oenothera), 

 fuchsia, garden balsam (Impatiens), garden rhubarb, etc. 



(l) For crystals of other types examine sections of prickly 

 pear (Opuntia), young basswood twigs, scales of onion, stem of 

 lamb's quarters (Chenopodium), petiole of beet, etc. These 

 are also composed of calcium oxalate. 



(m) Examine a thin cross-section of the leaf of the rubber 

 plant (Ficus elasiica). In some of the modified epidermal 

 cells will be found peculiar stalked crystalline bodies of calcium 

 carbonate deposited upon a cellulose core which hangs down 

 into the cell cavity from the outer portion of the cell wall. 

 Treat the section with hydrochloric acid. The cystolith, as it 

 is called, dissolves with the evolution of CO2, leaving the cellu- 

 lose core, thus distinguishing it from calcium oxalate, which 

 dissolves without effervescence. 



28. Cell Sap. The cytoplasm of a cell usually contains 

 a large amount of water imbibed by it but not really a 

 part of it. Water is also found fre- 

 quently in drops (vacuoles) within 

 the cell. This is the cell sap. It 

 holds in solution the various soluble 

 substances absorbed by the plant as 

 well as those manufactured by the 

 cell itself. It makes up by far the 

 greater part of the bulk of the contents 



^ of the average cell. Among the sub- fiq. 6.— Large vacuoles. 



i stances dissolved in the cell sap, in 



I addition to the mineral matters absorbed by the plant 

 from the soil water, are many sorts of organic compounds 

 produced by the cytoplasm. The most important of 

 these are the various sugars and organic acids. The 

 commonest of the sugars are saccharose or cane sugar 



