60 



BOTANY. 



alents of water of crystallization ([Ca 0] a C 4 6 -f 6 H 3 0). 



They may be simple (Fig. 47) or combined into compound 



crystals (Fig. 46) ; many of 

 the former are sometimes 

 found imbedded in the sub- 

 stance of the cell-wall of the 

 fibre-cells of certain Gymno- 

 sperms (Fig. 

 47). Simple 

 crystals oc- 

 cur also with- 

 the cell- 



Fig. 46. Crystals of calcium oxalate. 

 The right-hand portion of the figure 

 shows two raphis-cells of the Khubarb, 

 with their contained raphides, and one 

 crystal enlarged. On the left is a crys- 

 tal from the Deet. Much magnified. 



in 



cavities of 



many plants. 



The c o m - 



pound forms 



are very various ; they almost always 

 occur in cell-cavities, as in the beet (Fig. 

 46) ; and it not infrequently happens that 

 both simple and compound crystals are 

 found in the same plant, even in contigu- 

 ous cells, as is the case in the onion bulb. 

 80. Crystals of calcium carbonate 

 (Ca C0 3 ) occur less frequently than those 

 just described. Their most striking form 

 is that seen in the structures named cys- 

 toliths (Fig. 48). These possess a curious 

 structure ; a club-shaped or stalked out- 

 growth of cellulose projects into the in- 

 terior of a cell, and upon and in this mul- 

 titudes of small crystals are grouped. 

 Other forms of calcium carbonate crys- 

 tals are to be found in plants e.g., in the 

 Myxomycetes. 



According to some observers, crystals ceii c -wa?i 

 of calcium phosphate, calcium sulphate, ^a^-After Sachs, 

 and silica are occasionally to be met with in plants.* 



* See an article on plant-crystals by Dr. Lancaster in the Qr. Jr. of 

 Mic. Science, 1863, p. 243 ; also articles by Professor Gulliver in the 

 same journal for 184, 1866. and 1869. 



Fig. 47. Crystals of 



