192 



HOW CROPS GROW. 



In the root of the young bean, Sachs found a ring of cells, 

 containing crystals of sulphate of lime. (Sitzungsberichte 



der Wien. Akacl, 37, p. 106.) 

 Bailey observed in certain 

 parts of the inner bark of the 

 locust a series of cells, each 

 of which contained a crystal. 

 In the onion-bulb, and many 

 Fig. 24. Fig. 25. ot ] ier pl an ts, crystals are 



abundant. ( Gray s Struct. Botany, 5th Ed., p. 59.) 



Instances are not wanting in which there is an obvious 

 excretion of mineral matters, or at least a throwing of 

 them off to the surface. Silica, as we have see 1 .), is often 

 found in the cuticle, but it is usually imbedded in the cell- 

 wall. In certain plants, other substances accumulate in 

 considerable quantity without the cuticle. A striking ex 

 ample is furnished by Saxifraga crustata, a low European 

 plant, which is found in lime soils. 

 The leaves of this saxifrage are 

 entirely coated with a scaly in 

 crustation of carbonate of lime 

 and carbonate of magnesia. At 

 the edges of the leaf, this incrusta 

 tion acquires a considerable thick 

 ness, as is illustrated by figure 26, 

 a. In an analysis made by linger, 

 to whom these facts are due, the 

 fresh, (undried,) leaves yielded to 

 a dilute acid 4.14 | of carbonate 

 of lime, and 0.82 | of carbonate 

 of magnesia. 



linger learned by microscopic 

 investigation that this excretion of carbonates proceeds 

 mostly from a series of glandular expansions at the margin 

 of the leaf, which are directly connected with the sap-ducts 

 of the plant. (Sitz berichte der Wien. Akad., 43, p. 519.) 



