36 



Dr. M. J. Schleiden's Observations on 



primary simple cellular membrane have, on their first appear- 

 ance, everywhere as a foundation an arrangement in a spiral 

 band (or fibre) which becomes more or less distinct in various 

 ways ; and from this fundamental form are variously evolved 

 all the numerous modifications of the so-called vascular and 

 cellular walls, without, however, the one being to be regarded 

 as a transitory stage of the other — then we must undoubt- 

 edly ascribe to Valentin (Repertorium, Part I.) the merit of 

 having first advanced this doctrine in all its generality. 



For along with those theories, observation had pursued 

 her quiet course, and had found the porous and spiral forma- 

 tions in the cellular tissue also, and had gradually extended 

 her discoveries so far, that at present it would perhaps be diffi- 

 cult, at least in the Phanerogamia, to point out any consider- 

 able masses of completely developed cellular tissue which do 

 not manifest distinct traces of these textures. 



I will here give a brief view of this doctrine from inquiries 

 of my own, in which I lay claim to nothing new, more than 

 those acquainted with the subject will ascribe to me ; but, on 

 the other hand, I dispense with the trouble of everywhere 

 enumerating my authorities. 



The cells of plants, including the so-called vessels, but 

 with the exclusion of the laticiferous vessels*, the reducing 

 of which to cells is still not at all clear to me, allow of 

 two periods being distinguished in their life. In the first, 

 that of their origin and isolated independent development, 

 the membrane forming them grows, in its entire substance, 

 by true intussusception. But as soon as the cells have ad- 

 hered to form the cellular tissue and constitute the mass of a 

 certain plant or its parts, this mode of growth either ceases 

 entirely, or recedes so far into the background, that, from my 

 observations up to the present time, I cannot venture to 

 maintain its continuance ; but neither can I deny it on 

 account of the frequently very considerable expansion of the 

 cells after the appearance of the succeeding formations. But 

 in every case at present a new and by far predominant mo- 

 mentum is added, viz. that a new layer is deposited on the 

 inner surface of the cellular wall, and indeed everywhere, in 

 the form of one or more spiral closely wound bands, so that 

 the coils, without continuity inter se, still mostly exhibit the 

 completest contiguity. From personal observations, which, 

 however, are still too imperfect to be detailed here, I think I 

 may venture to conclude that originally there are always at 



* Moreover, the old milk vessels of the leafless Euphorbia exhibit a com- 

 position of layers and spiral stripes exactly as the cells of the liber in the 

 Apocyne<e> 



