124 THE PHENOMENON OF 



out, interposing a boundary structure, the cell-membrane, 

 as a medium for the intercourse with the external world, 

 and a protection from direct attack. Although the plant 

 be developed almost infinitely through the unlimited 

 nature of the process of sprouting, its life appears in 

 every cell (with a few exceptions) as in a circumscribed 

 and in a peculiarly inwardly determined sphere of forma- 

 tion, so that the cell also is, in a certain sense, an indi- 

 vidual, and, in fact, has been pre-eminently regarded as 

 the individual of the plant by many authors.* 



As the single plant begins with a simple cell, so does 

 the Vegetable kingdom. In the lowest stage of this the 

 plant presents itself as a simple cell, and the first repe- 

 tition of cell -formation is, at the same time, propagation. 

 The farther we trace up the stages of the Vegetable 

 kingdom from this point, the greater is the multiplicity 

 of the division of the originally simple sphere of life into 

 subordinate spheres, and the more frequently is the cell- 

 formation repeated : the vegetable organism becomes 

 multi-cellular. While the cell constitutes actually the 

 sole individual of the plant in Uni-cellular plants, in 

 the higher plants it becomes a sphere of formation sub- 

 ordinate to the more developed individual organism. 

 With the less perfect organisation of the plant, as com- 

 pared with that of the animal, with its peculiar deficiency 

 in a permanent and thoroughly pervading central relation 

 of the parts, the vegetable cell, as a subordinate part of 

 the organism, possesses a far greater individual independ- 

 ence than the cell of the animal tissue, manifoldly changed 

 in its structure, and more insolubly connected to the 

 whole. 



Unicellular plants, in the strictest sense, are repre- 

 sented properly only by those in which the whole cycle 

 of life is completely shut up in one cell, the first recon- 

 struction or division being at once the commencement of 



* Schleiden, ' Grundriss der Bot., 5 p. 28, and 'Grundziige,' 11, p. 4. 

 ('Principles of Sc. Botany,' London, 1849, p. 126.) 



