48 BOTANICAL MICROTECHNIQUE. 



tures. In fact, the precipitate of sulphur which is formed 

 when dilute hydrochloric acid is added to a solution of 

 calcium pentasulphide shows the same relations, on micro- 

 scopic examination, as the sulphur granules of the Beggia- 

 toas. It is possible, according to Winogradsky, that these,, 

 as well as the granules of the precipitated sulphur, gradually 

 pass over into the solid condition, and that, especially in 

 slowly growing threads, all the stages from the fluid to the 

 almost solid condition occur. 



70. It should be observed here that Jonsson (I) has seen 

 in a mycelium of Penicillium, growing on dilute sulphuric 

 acid, strongly refractive bodies which correspond in many 

 of their reactions with the sulphur granules of the Beggia- 

 toas, and consist, according to Jonsson, of a mixture of sul- 

 phur and an oil-like substance. 



4. Hydrochloric Acid, HC1, and its Salts. 



71. For the recognition of hydrochloric acid Schimper 

 (II, 212) found the two following methods especially useful. 



I. The addition of silver nitrate causes the formation of 

 amorphous silver chloride, but this may be obtained in crys- 

 talline form by dissolving the precipitate arising from the 

 addition of silver nitrate in as little ammonia as possible and 

 allowing the fluid to evaporate. Regular crystals of silver 

 chloride are thus formed, consisting chiefly of hexahedra, 

 octahedra, and rhombic dodecahedra, as well as combina- 

 tions of these (cf. Fig. 19). These 

 ^^ ^^^ crystals gradually become violet-col- 

 __ ^ff *y. \f &p ore d m tne light 5 Dut m the presence 

 ^ re< ^ ucm S plant-juices they often be- 

 \y come very rapidly colored. Formed 

 silver chloride may also be recognized 

 FIG. 19. -Crystals of silver by its ready solubility in potassium 



chloride. After Haushofer. J J J 



cyanide, in sodium hyposulphite, and 



in a concentrated solution of mercuric nitrate. It is also 

 somewhat soluble in concentrated solutions of the alkaline 

 metals and in concentrated hydrochloric acid ; and, accord- 



