220 THE PHENOMENON OF 



to the factis known about it, we can in like manner 

 perceive nothing else than a periodical interruption of 

 the diurnal process of formation, by a process of deforma- 

 tion and de-carbonisation, although this does not so 

 profoundly affect the plant. It is true we cannot observe 

 in it any perceptible solution of cell-membrane, starch 

 granules, and the like, but there is no doubt of the 

 occurrence of an interruption in the deposition of these 

 structures, probably through the interposition of a process 

 of combustion of the materials out of which they 

 originate, while still dissolved in the cell-sap. It is 

 indeed not very adventui-ous to refer the lamellar depo- 

 sition of the cell-membrane, and the concentrically 

 laminated structure of the starch-grain, to this daily 

 periodicity of the cell-life. The great number of layers 

 which may be distinguished by suitable treatment in the 

 cell-membrane even of plants of short life {liydrodictyon, 

 Cladojjhora, Botrydimii), is not opposed to the assumption 

 that they are diurnal layers, and it is imaginable, under 

 this hypothesis, that bright and dull days, as well as the 

 age of the cell and other circumstances, may effect im- 

 portant modifications in reference to the formation of 

 distinguishable layers. Annual rings, or better, annual 

 layers, may doubtless be demonstrated in cells of perennial 

 duration. The lamination described by Mohl,* in the 

 walls of liber-cells, for instance of -Cocos and Calamus, 

 which exhibit the peculiar phenomenon, that the thick 

 and not very numerous layers, which are separated from 

 each other by dilute sulphuric acid, are composed of an 

 outer, broader, and softer, and an inner, thinner and 

 firmer layer, may perhaps be compared with the condition 

 of the annual rings of the wood of Dicotyledons, in 

 which, in correspondence with the reverse order of 

 formation, each yearly ring exhibits an inner, broader, 

 and looser, and an outer, narrower, and denser half. I 



» ' Botaiiisclie Zuituiig,' ISt-l, p 309, t. ii, figs. S, 3.5, 'iO. (Trans 

 ^ yeienliflc Memoirs,' vol. iv, p. 103, pi. i, ii, figs. 8, 2.5, ^'(i.) 



