THE VEGETABLE CELL. 7 



different organised structures found in plants and animals originate 

 directly or indirectly by means of elementary corpuscles, which have 

 been named " cells." These so-called cells, remaining as separate cor- 

 puscles in the fluids, and grouped together in the solids, persisting in 

 some cases with but little change, in others undergoing a partial or 

 thorough transformation, produce the varieties of form and structure 

 met with in the animal and vegetable textures. Nay, the germ from 

 which an animal originally springs, so far at least as it has been 

 recognised under a distinct form, appears as a cell ; and the embryo, 

 in its earliest stages, is but a cluster of cells produced apparently from 

 that primordial one ; no distinction of texture being seen till the 

 process of transformation of the cells has begun. 



Xo branch of knowledge can be said to be complete ; but, even now 

 that between a quarter and half a century has elapsed since the pro- 

 mulgation of the cell-doctrine, there is, perhaps, none which can be 

 2nore justly regarded as in a state of progress than that which relates 

 to the origin and development of the textures, and much of the current 

 opinion on the subject is uncertain, and must be received with 

 caution. 



Fig. 1. 



THE VEGETABLE CELL. 



If we view under the microscoj^e the early embryo of one of the 

 higher plants (fig. L), we see that it is built up entirely of a number 

 of closely adherent vesicles, — these are 

 the elementary cells. Each of those cells 

 consists of an external membranous invest- 

 ment (a), the cell-wall, containing in its 

 interior a finely granular transparent sub- 

 stance of semi-fluid consistence — the proto- 

 plasm (5), — in this is imbedded at one part 

 a more solid looking body of rounded form 

 (the nucleus, c), which again itself con- 

 tains generally one or two distinct strongly 

 refi-acting particles {nudeili). On closer ex- 

 amination it may be observed that in many 

 cells the protoplasm is not absolutely quies- 

 cent as at first sight appears, but on the 

 contrary exhibits slow streaming movements 

 of its substance, indicating a certain amount 

 of vital activity. This is more particularly 

 the case in the more rapidly growing parts, 

 where also it is not uncoimnon to find two 

 nuclei in a cell. This, as will be seen later 

 on, is an indication of the commencing 

 division of the cell into two : by the con- 

 stant repetition of this process the growth 



oi the plant is effected. In their early condition all plants are 

 similarly comjwsed of an agglomeration of cells, and some retain this 

 primitive condition throughout life ; in all the higher classes, however, 

 by changes in the form and in the contents of the cells, various modifi- 

 cations occur, by means of which the different textures of the plant 

 are produced. Some of these are shown in the accompanying figures 



Fig. 1. — Embryo of a Dico- 

 tyledonous Plant. Mode- 

 rately Magnified. 



a, cell-envelope ; h, proto- 

 plasm; c, nucleus. 



