2 ANATOMY AND PHYSIOLOGT OF 



(" Physioloy.''' i. 64), altliongb Sprengel, Ruclolphi, Link, and Kieser had 

 already recognized that they all were modifications of the cell. Far less 

 than this was the true nature of the vessels perceived hj the earlier phy- 

 totomists j and I believe that I was the first to detect their origm from 

 rows of closed cells [^^ Memoirs of the Acad, of Munich^' i. 445. De struc- 

 tura imlmcwum, § 26 — 39). ISTo sharply defined line can be drawn be- 

 tween vessels and cells, for reasons which will be hereafter discussed. 

 Whether the milk-vessels^ which indeed occur only in a comparatively 

 small portion of plants, and play a very subordinate part both in ana- 

 tomical and physiological relations, originate in an analogous manner from 

 rows of cells, or are to be regarded as a system essentially cliiferent from 

 the rest of the elementary organs, is a question upon which no opinion 

 has yet acquired an universal acceptance. Unger asserts the former 

 (^^ Annals of the Vienna Museum^' ii 11) ; but it is more than doubtful 

 whether his observations were accurate, and it seems that the milk- vessels 

 ought to be regarded as membranous Imings of passages wliich appear be- 

 tween the cells. {See an anonymous memoir in the ^^Botanische Zeitumj^'' 

 1846, 833, entitled "The Millc- vessels : thek Origin, t&c") 



The basis of the substance of all vegetables consists of tlie 

 cells, since even in the most highly developed plants all the 

 organs are in the youngest condition com|)osed of cells alone, and 

 the vessels only appear during the subsequent development. In 

 the lower plants (Fungi, Algse, Lichens, Liver-mosses and Mosses) 

 all the elementary organs persist in the organization of the cell. 



Ohserv. The circumstances, that a plant is composed of cells alone, or 

 also possesses vessels, have not that importance either in a systematic or a 

 pLysiological pohit of view wliich De CandoUe attributed to them, when he 

 used them for the piimary division of tbe vegetable kingdom^ into Cellular 

 and Vascular plants, for these condition^) do not run parallel with the total 

 organization of plants, since there exist both Cryptogamic and Phanero- 

 gamic plants with and without vessels. 



I THE ANATOMICAL CONDITION OF THE CELL. 



A. POKM OF CELLS. 



The forms under which cells present themselves are so manifold, 

 that a special examination of all would occupy a far greater space 

 than can be devoted to it in this place ; I therefore confine my- 

 self to a few observations. 



In the first place, in examining the form of the cell, we have to 

 take notice that it depends upon two circumstances. On one hand 

 the form of the cells is determined, like that of every organic 

 body, by its indwelling laws of development ; on the other hand, 

 the individual cell, in the fixr greater majority of cases, cannot 

 follow those laws uninterruptedly, because it forms part of a com- 

 pound tissue, and is compelled by its intimate connexion with the 

 surrounding elementary organs, to accommodate itself to the space 

 thus determined for it, and in consequence of the pressure to 

 which it is exposed laterally from the surrounding elementary 



