106 



is meant. When slaked by the addition of water the chemical 

 union that is immediately set up gives rise to the development of 

 considerable heat. 



Another important combination of lime is the oxalate of 

 lime. This is widely found in plants, and as it is largely concerned 

 in the economy of plant life, we shall make further reference to 

 it. In the meantime we may accept it as generally understood 

 that all mineral substances, such as lime, potash, silica and others 

 can only be introduced into plants after they are completely dis- 

 solved in water. The delicate root hairs that are in direct contact 

 with particles of soil absorb moisture (or what may be popularly 

 called soil juice) and the crude sap passes upward through the 

 cell membranes into the stem and leaves. Afterwards when the 

 various substances contained in the sap are fully elaborated into 

 suitable food-material in the leaves, they then descend and serve 

 to build up the structure of the plant, and maintain its several 

 activities, including the ultimate production of fruit and seed. 



Lime easily dissolves in water, and thus it is absorbed by the 

 root hairs, and found in nearly all parts of plants. An acid that 

 readily combines with lime, found plentifully, in such plants as 

 wood sorrel and varieties of Rumex, also in rhubarb and various 

 lichens, is the oxalic acid already referred to. It is probable 

 that a large part of the lime found in the tissues of plants is 

 precipitated by this oxalic acid and remains inactive. According 

 to Sachs, " the chief importance of lime in plants must be sought 

 in its serving partly as a vehicle for sulphuric acid and phosphoric 

 acid in the absorption of food material ; and partly in its fixing 

 the oxalic acid, which is poisonous to plants, and rendering it 

 harmless." Elsewhere Sachs states this in another form: — 

 " Calcium dissolved in water is introduced into plants in combina- 

 tion with sulphuric acid as calcium sulphate. This when decom- 

 posed sets free the lime which combines with oxalic acid to form 

 insoluble calcium oxalate. The sulphuric acid goes to form the 

 sulphur which is used in the production of albuminous substances 

 or proteids. Lime is therefore important to plants, inasmuch as it 

 is a medium of transport of sulphur." It might be added that 

 without the albuminous substances or proteids just referred to 

 plants would be unable to yield the nutritive food-substances which 

 render them acceptable sustenance for man and beast. 



Lime Deposits in Trees and Coco Nut Pearls. 



That lime in some form exists in the cells and tissues of plants 

 can be abundantly proved. For instance, what may be regarded 

 as excess deposits of carbonate of lime, have been found in the 

 wood of a number of Dicotyledonous trees usually blocking the 

 •cavities of vessels here and there or sometimes forming more 

 extensive accumulations entirely filling the cavities of vessels, 

 fibres, parenchyma cells, etc., over considerable tracts of wood. 

 Such deposits may be seen in heart-wood, or in knots, or in dead 

 wood due to wounding. Examples of the species in which 



