Biblioffrajikical Notices. 315 



Alex. Brauu, one of the most profound of modern vegetable phy- 

 siologists, says, " From the contents («. e. the primordial utricle with 

 its contents) all the vital activity of the cell proceeds ; the membrane 

 is an externally deposited structure, a product of secretion, which 

 takes only a passive share in the vital actions, as the medium of ex- 

 change between the interior and the exterior, at the same time sepa- 

 rating and uniting the neighbouring cells, and affording defence and 

 solidity to the separate cell in connexion with the whole tissue .... 

 Thus the hfe of the plant weaves in the cell-membrane its own 

 shroud, and dies at last in the dwelling it has constructed for itself." 

 (Ueber Verjungung, p. 166.) 



Schacht (Die Pflanzen-Zelle) as decidedly advocates the same 

 view, and so far as we know, it is that adopted in all the ordinary 

 text-books ; in these we universally find it assumed or stated, that 

 the cellulose membrane of the cell is a passive element excreted and 

 formed by the primordial utricle, and possessing no powers inde- 

 pendent of it. 



Von Mohl, however, speaks far more cautiously on this head ; in 

 his present work, p. 36, we find : — 



" In all young cells, whatever their subsequent contents may be, 

 whether they persist in the stage of cells or become changed into 

 vascular utricles, a series of formations are met with, which disappear 

 again more or less perfectly in the subsequent periods of hfe, and 

 which stand in the closest relation to the origin and growth of the 

 young cell, but only in particular cases in relation to their later func- 

 tions .... The primordial utricle disappears again vrith the thick- 

 ening of the vessels, the cells of the wood of the pith of the inner 

 part of the petiole, and of thick leaves " (p. 36-37). And the fact 

 of the early disappearance of the primordial utricle in many cases 

 was equally pointed out in his earlier work, " Remarks on the Struc- 

 ture of the Vegetable Cell," 1844 (Taylor's Scientific Memoirs, iv. 

 91). _ Now a slight consideration must we think render it evident, 

 that if it be true that the primordial utricle disappears with the 

 thickening of the cellulose membrane, the latter continuing to grow 

 subsequently to its disappearance, it cannot be that the primordial 

 utricle is the sole active agent in the growth of the plant ; the cel- 

 lulose membrane must have its power of growth and independent 

 activity also. 



That such is indeed the case is we think evidenced in the most clear 

 and striking manner by the development of the peculiar spirally 

 thickened and perforated cells in the leaf of Sphagnum, which is 

 so well described by Schacht {I. c. 66-67), whose observations (the 

 full bearing of which he does not seem to see) we have taken occa- 

 sion to verify in every particular. We have no space to enter into 

 details in this place, but we may shortly state that certain cells, at 

 first perfectly resembling the rest of those which constitute the base 

 of the leaf of Sphagnum, enlarge disproportionately, and gradually 

 lose every trace of contents and primordial utricle. Iodine, sul- 

 phuric acid and sugar, and other reagents which yield abundant evi- 

 dence of the primordial utricle in the surrounding cells, fail to pro- 



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