108 



Continuing our investigations, we find lime occurring in fine 

 granular deposits in the cells of living plants. Also in rounded 

 grains in others. In the epidermal cells of the leaves of fig and 

 mulberry trees and in hops are deposited clusters of very small 

 microscopic crystals of carbonate of lime known as cystoliths. 

 Nearly all other crystals found in plants consist of oxalate, not 

 carbonate of lime. Those appearing like bundles of needles are 

 known as raphides. Some of these are microscopically of large 

 size and beautiful with perfectly formed crystalline surfaces. Such 

 crystals are found in the cavities of cells in the leaf stalks of 

 begonia and in the stem and root of the haricot bean. In lilies 

 and aroids crystals of oxalate of lime in the form of raphides are 

 found filling many of the large elongated cells. 



It is interesting to note in the case of the calcium oxalate 

 stored up in great quantity in the leaves at the end of summer 

 that the throwing off of the foliage in the case of deciduous trees 

 and shrubs must be really regarded as a method of removing 

 waste materials and may be compared to the excretion of waste 

 which occurs in animals. It is only the framework of empty 

 cells — the dead envelopes of the living portions of the plant — 

 which is thrown away. The valuable carbo-hydrates and 

 albuminous materials — in fact everything which is of use to the 

 plant, have already been conveyed from the leaf blades into the 

 woody branches or subterranean root stocks and there deposited 

 in places where they find a safe resting place and can survive the 

 drought of summer or cold of winter unharmed. 



Lime Dissolved and Accumulated by Plants. 



There are striking instances where the roots of lichens and 

 mosses by the exudation of carbonic acid have corroded and 

 etched hard surfaces and caused rough and uneven depressions. 

 There are chemical as well as mechanical influences at work. A 

 growing rootlet penetrates wherever the merest particle of lime 

 has been dissolved and accomplishes regular mining operations. 

 Projecting particles of the carbonate not yet dissolved are 

 separated by mechanical pressure of the roots from the main 

 mass, and tiny loose fragments of the lime are to be seen, which 

 are washed away by the next shower or else carried off as dust by 

 the wind. 



The roots of the higher plants also produce similar results. 

 This may be proved by sowing seeds in a layer of sand on a 

 polished slab of marble. The roots of the seedlings creeping 

 closely in contact with the stone cause markings as though the 

 latter had been etched. A solution of individual particles of 

 lime takes place under the influence of the acid juice saturating 

 the cell walls of the roots. Such markings are quite distinct and 

 can be seen by the naked eye. 



Still more striking is the accumulation of lime by the agency 

 of water plants in streams and lakes. In water loaded with 

 bicarbonate of lime a number of mosses become encrusted with 



