316 Bibliographical Notices. 



duce the slightest characteristic reaction in these. But tracing these 

 enlarged cells in their course towards the point of the leaf, we find 

 that, first, a very considerable spiral or annular thickening band is 

 developed from their ovules ; and secondly, that these walls become 

 perforated in particular localities, showing clearly that the cellulose 

 wall is in itself abundantly competent to perform the vital actions of 

 assimilation and absorption, or rather resolution, without the assist- 

 ance of the primordial utricle. 



Nor let it be said, that here the thickenings and resolutions are 

 determined by the primordial utricles of adjacent cells, for the Sphag- 

 num leaf, as is well known, consists of only a single layer of cells 

 joined side by side, and the thickening takes place as much on the 

 upper and lower surfaces as on the sides of the spiral cells, while the 

 perforations are formed exclusively upon the upper and lower sur- 

 faces. Surely here nature furnishes us with a crucial instance of the 

 independent vitality and powers of action of the cellulose cell-wall, 

 whence important conclusions may be drawn for the whole vege- 

 table kingdom. 



There is yet another error which we venture to submit pervades 

 the whole of vegetable no less than animal physiology, — we refer to 

 the notion that animals and plants are formed by the coalescence 

 of their histological elements — the cells. It is said that plants are 

 formed by means of cells which have "grown together^' (Von Mohl, 

 p. 30), having "arisen separately as development teaches " (Schacht, 

 p. 75) ; and this conception of the individuality of the separate plant- 

 cells, though by giving distinctness to the ideas of investigators it 

 has served a good purpose, seems to us to be at present essentially 

 obstructive. 



If in fact we turn from this convenient mode of viewing the facts 

 to the facts themselves as they really are, we find that the cells which 

 compose any vegetable tissue never have been independent, and that 

 therefore it is as absurd to talk of their coalescence, as to say that a 

 man is formed by the coalescence of his head, trunk and limbs. 



Indeed, all the knowledge we have hitherto obtained of develop- 

 ment, whether morphological or histological, uniformly bears testi- 

 mony to the truth, that the great law established by Von Bar for the 

 animal world holds good as universally in that of plants. They and 

 all their organs, and all the histological elements of these organs, are 

 produced, not by the coalescence of the heterogeneous, but by the dif- 

 ferentiation of the homogeneous parts, and it would be more true to 

 say that the plant is formed by the separation of cells than that it 

 arises from their coalescence. This however is a most important 

 subject, and one which we hope to follow out elsewhere. 



Handbuch der Conchyliologie und Malacozoologie. 

 Von Dr. R. A. Philippi. Halle, 1853. 8vo, pp. 548. 



By the preface we are informed that this work was written on 

 board the Hamburg brig Bonito, and dated while it was passing 

 Cape Horn, the author having, by the late political disturbances in 



