Keegan : The Chemisivy of some Common Plants. 431 



and also a tannoid or tannin which is iron-greening and pre- 

 cipitates gelatine ; both of these constitnents being originally 

 present in the cell-wall as compounds (esters) of cellulose. 

 The iinparalled local, geographical, and climatic distribution 

 of mosses is evidently indissolubly connected with the mar- 

 vellous structure, and constitution of the skeletal framework 

 of the cell. 



Common Reed {Pliragmites eommiinis) — This plant forms a 

 sort of hedge by the margins of lakes and in marsh}' places. 

 ' The wavy swell of the soughing reeds ' is a spectacle familiar, 

 to the wanderer in these haunts. This grass belongs to the 

 tribe Festuceae, which also includes many of the abundant and 

 familiar species of our meadows and pastures. The rootstock 

 is thick, jointed, and extremely creeping, it contains much sugar, 

 is very nutritious, and has 6 per cent, pure ash yielding 57.7 

 silica according to Fittbogen. The leaf is traversed by a large 

 number of nerves highly scleriiied and lignified, and is protected 

 also by bands of sub-epidermal fibres, with verv thick walls ; 

 the organ exhibits great power of transpiration. On 20th 

 August the dried blades yielded about 2 per cent, wax, with 

 much carotin ; this wax forms a fine closely adherent layer on 

 the lower epidermis, and contains a solid hydrocarbon, so that 

 it rapidly separates from boiling alcohol ; little or no chloro- 

 phyll was withdrawn from the leaf bv boiling benzene, or bv 

 boiling acholol alone, it is only when the leaf is first extracted 

 by benzene and then boiled in alcohol that the green pigment 

 is dissoh'ed in great 'quantity, depth, and intensity. The alco- 

 holic extract (after benzene) contained a distinctixe quantity 

 of a tannoid which seems to be quercetin or fisetin, it exhibits 

 great tinctorial power, the reactions with iron, lead, and alum 

 salts being unusually clear and brilliant ; there was no tannin 

 or free phloroglucin, but cane-sugar was indicated, and a large 

 quantity of a resinous substance which dissolved in sulphuric 

 acid with a deep brown colour passing to a splendid \-iolet. 

 There was a good deal of pectosic mucilage and reserve starch 

 (unextractible), and crude fibre (52.4 per cent.), but no oxalate 

 of calcium. The ash of the leaf amounted to 7.4 per cent., and 

 contained 20 per cent, soluble salts, 45.4 silica, 10.4 lime, 4.8 

 P^0'\ 3.7, SO'^ and 4 chlorine; there was a good deal of 

 manganese, but no soluble silica or carbonates. The foregoing 

 analysis throws clear light on the phenomena of grassy vegeta- 

 tion. We see how thoroughly the chlorophyll is ' protected ' 



1909 Dec. I. 



