of Organic Bodies. 181 



On comparing the constituents of the ash of peas with those 

 of rape-seed, we find that the aqueous extract of the car- 

 bonized peas differs essentially from that of the carbonized rape 

 in the large amount of alkaline chlorides which it contains, 

 and which are present in very small quantity in the rape, 

 whilst the latter contains more phosphate of potash than the 

 former. The muriatic extract of the carbonized rape also 

 contains much more phosphoric acid than that of the peas, 

 whilst the anoxidic portion of the carbonized mass of the peas 

 yields more phosphoric acid than that of the rape. The in- 

 organic constituents of the pea- and the rape-straw are how- 

 ever very similar to each other. 



Appendix V. 



On the Amount of Silica contained in some Plants. 

 By M. Struve. 



As is well known, the stems of the Equisetace^e when incine- 

 rated leave a residue consisting of almost pure silica, which 

 retains the form of the original stem. It fuses before the 

 blowpipe on charcoal. If this residue be exhausted, first with 

 water and then with muriatic acid, which dissolve very small 

 quantities of alkaline salts, among which we find phosphoric 

 acid, together with sulphate and phosphate of lime, it no 

 longer fuses before the blowpipe. The ash of the following 

 species of Equisetum^ after treatment with water and acids, 

 yielded the following composition : — 



The epidermis of the stolones of Calamus Rhodayi, the 

 Spanish cane, which may be easily separated by repeatedly 

 bending them, consists almost entirely of silica, whilst the 

 woody substance itself contains mere traces of it. Muriatic 

 acid does not remove either alumina or other bases, excepting 

 a very small quantity of lime. This silica does not fuse before 

 the blowpipe. After treatment with muriatic acid, it had the 

 following composition : — 



Silica . . . 99-20 

 Lime . , . 0-45 



99-65 

 Spongia lacustris, from the neighbourhood of Berlin, also 



