262 Miscellaneous. 



membranous sac consisting at first of pure cellulose, and distinguished 

 by no particular organic structure, lined with one or more coats, in- 

 volving proteine constituents, and indicating more or less perfectly a 

 spiral arrangement or order of growth, may be considered as convey- 

 ing a tolerably clear notion of the organisms of which vegetables are . 

 in great measure composed. Some botanists have, however, doubted 

 the simplicity of structure of the outer membrane, and instances more 

 or less adverse to the view occur in works on botanical physiology, 

 and in introductions to the study of vegetables ; but none perhaps of 

 greater weight than the instance so beautifully represented by Kiitzing, 

 in Schizosiphon gypsophilus, and which has been verified by many 

 observers of the more minute freshwater Algse. In all such cases, 

 however, it is doubtful whether the external membrane is not ruptured, 

 and whether its supposed constituent threads do not really belong to 

 a second membrane, and unfortunately chemical tests have not at 

 present been sufficiently applied to the elucidation of the point. 



The question has again very recently been mooted by the younger 

 Agardh, who has published a small tract in quarto, printed at Lund, 

 entitled " De Cellula Vegetabili Fibrillis tenuissimis contexta." His 

 observations do not at all satisfy us as to the compound structure of 

 the external membrane, and are' at present too confined and imperfect 

 to warrant the assumption of any general law ; they are however so 

 curious, and propose such an interesting field for further inquiry, that 

 we think it almost imperative to call our readers' attention to the sub- 

 ject. The plants which came under his observation were principally 

 Conferva Melagonium, remarkable amongst British species for the 

 size of its articulations, though surpassed in this respect by such exotic 

 species as C. clavata, together with Griffithsia equisetifolia and Poly- 

 siphonia complanata. lu the first more especially he found fascicles 

 of fibres, more or less felted with each other, passing from cell to cell, 

 and by means of the diaphragm from the internal membrane of one 

 cell to that of the cells in immediate contact or continuance with it, 

 and leaving spaces between the fascicles threaded and traversed by 

 finer fibres, with very faint and obscure traces of a connecting gela- 

 tinous or submembranous substance. These fibres were especially 

 evident when the walls were ruptured, and appeared to be solid, with- 

 out any canal. In the Polysiphonia he found the fibres separating 

 from the main wall of the cells, and forming little swollen prominences, 

 which he considered to be the commencement of new cells, and the 

 rudiments of the cells external to the well-known radiating vesicles 

 of the main stem. 



We are unable to verify the structure represented by Agardh ; but 

 as the Conferva and Griffithsia are by no means rare, it cannot be 

 difficult to procure fresh specimens to enable us to do so. Meanwhile, 

 though we cannot doubt the accuracy of M. Agardh, and are ready 

 to acknowledge our obligations to him for pointing out so curious a 

 matter, many considerations prevent us from entertaining a notion that 

 the structure is at all general. It is quite impossible, for instance, 

 that in such cases as Zijgnema, the constituent fibres of the diaphragm 

 of continuous cells, if such exist, can pass from one into the other in 

 the manner rejiresented in C Melagonhun. A glance at Schleiden's 



