STROyO DRINK AND TOBACCO SMOKE. 23 



formidable appearance (Plate 4, fig. '1Q>). They are most 

 numerous on the green awns of the seed, where they may 

 be seen in all stages of development (Plate 4, fig, 28 h). 

 A remarkable feature in the growth of our plants is 

 the power they possess of absorbing frc)m the soil, and 

 secreting in their tissues, a very large amount of silica, 

 the basis of fiint-stones and of glass, Tn the ashes of 

 barley straw De Saussure, a French chemist, found 57 

 per cent, of this substance ; more recently our own 

 illustrious chemist, Fownes, has given the analysis of 

 straw from Ijarley grown in Battersea Fields. When 

 burned, it yielded 6 "9 7 per cent, of unconsumed ashes. 

 These ashes, on analysis, yielded in the soluble portion 

 of them : — • 



Sulphate of potash 16 "6 per csiit. 



Chloride and little silica 0-4- 



11 



In the insoluble portion : — 



Siliceous scales 70 -5 



•> 



Phosphates of lime and m igUf.-i.i . . 8'5 



Carbonate of lime 2 



Alkali, magnesia, and loss 15 ,, 



Water ."» 



1) 



5) 



lUO-0 



Of this silica, 87 per cent, was uncombined with any 

 earthy or alkaline base. 



Under the blow-pipe this silica may be made to fuse 

 into a glass of topaz-yellow colour. L^ider the micro- 



