THE ASS OF PLANTS. 207 



Cters. Around the borders are seen the scales of carbonates ; some of 

 these have been detached, leaving round pits on the surface of the leaf : 

 c, d exhibit the scales themselves, e in profile : ft shows a leaf, freed 

 from its incrustation by an acid, and from its cuticle by potash-solution, 

 so as to exhibit the veins (ducts) and glands, whose course the carbon- 

 ates chiefly take, in their passage through the plant. 



Further as to the state of ash-ingredients. It ia 

 by no means true that the ash-ingredients always exist in 

 plants in the forms under which they are otherwise famil- 

 iar to us. 



Arendt and Hellriegel have studied the proportions of 

 soluble and insoluble matters, the former in the ripe oat 

 plant, and the latter in clover at various stages of growth. 



Arendt extracted from the leaves and stems of the oat 

 plant, after thorough grinding, the whole of the soluble 

 matters by repeated washings in water.* He found that 

 all the sulphuric acid and all the chlorine were soluble. 

 Nearly all the phosphoric acid was removed by water. 

 The larger share of the calcium, magnesium, sodium and 

 potassium compounds was soluble, though portions of each 

 escaped solution. Iron was found in both the soluble and 

 insoluble state. In the leaves, iron was found among the 

 insoluble matters after all phosphoric acid had been re- 

 moved. Finally, silica was mostly insoluble, though in 

 all cases a small quantity occurred in the soluble condi- 

 tion, viz., 3-8 parts in 10,000 of the dry plant. (Wach- 

 sthum der Haferpflanze, pp. 168, 183-4. See, also, table 

 on p. 171). 



Weiss and Wiesner discovered by microchemical in- 

 vestigation that iron exists as insoluble ferrous and ferric 

 compounds both in the cell-membrane and in the cell- 

 contents. (Sitzungsberichte der Wiener Akad., 40, 278.) 



Hellriegel found that in young clover a larger propor- 

 tion of the various bases was soluble than in the mature 

 plant. As a rule, the leaves gave most soluble matters, 

 the leaf stalks less, and the stems least. He obtained, 



*To extract the soluble parts of the grain in this way was impossible. 



