60 



BOTANT. 



1 



Mg. 46. — Crystals of calcium oxalate. 

 The right-hand portion of the figure 

 shows two raphis-cells of the nhiibarb, 

 with their contained raphides, and one 

 crystal enlarged. On the left is a crys- 

 tal from the beet. Much magnified. 



alents of water of crystallization ([Ca 0], 0, 0^+ 6 H, 0). 

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



crystals (Kg. 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. ^j 



47). Simple 

 crystals oo-J 

 cur also with- 

 in the cell- 

 cavities of 

 many plants. 

 The c m - 

 pound forms 

 are very Tarious ; 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 CO3) 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 ^^^T^^.^ 

 of calcium phosphate, calcium sulphate, ™™5i«s.-Arter 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 

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

 same journal for 18R4, 1866. and 1869. 



■pig. 47.— Crystals of 



