.66 



BOTANICAL MICROTECHNIQUE. 



'still as uncertain as the molecular formula of the calcium 

 phosphate contained in the sphaerocrystals. 



g. Recognition of Calcium in the Ash. 



98. For this purpose Schimper (II, 211) recommends 

 especially the sulphuric acid reaction, which may be con- 

 ducted by dissolving the ash directly in about 2% sulphuric 

 acid and then letting it dry slowly. There are thus pro- 

 duced, especially at the edge of the drop, crystals of gyp- 

 sum which belong to the mono- 

 clinic system. Among these, 

 plate-like crystals, whose obtuse 

 angle (or, Fig. 24) measures 127 

 31', according to Haushofer (I, 33), 

 are especially characteristic. Be- 

 sides, twin crystals are very nu- 

 merous, whose edges form an angle 

 of 104 or of 130 with each other 

 (cf. Fig. 24). But the most various 

 fusions are also found, on whose 

 projecting ends pretty accurate 



.determinations of the angles may be made. 



The crystals of gypsum are also distinguished by the fact 

 that they are transformed instantly into small needles on 

 heating in concentrated sulphuric acid. The masses of 

 needles preserve the form of the original crystal, but appear 

 quite opaque if of much thickness. These needles may 

 probably represent the anhydrite of gypsum. 



If calcium is present in the ash as calcium sulphate, it 

 Avill, of course, form its characteristic crystals if the aqueous 

 solution of the ash is allowed to slowly evaporate. 



h. Recognition of Calcium in the Cell-sap. 



99. For the recognition of calcium in the cell-sap, Schim- 

 per employed chiefly the two following reactions : 



i. On the addition of ammonium oxalatc, calcium oxalate 

 !.} formed in the cells containing calcium, in the form of 



"Fie. 24. Crystals of calcium sul- 

 phate. After Haushofer. 



