SECTION 1G.] 



ANATOMICAL STRUCTURE. 



131 



solid matters and in age mostly air — naturally came to be named a Cell. 

 But the name was suggested by, and iirst used only for, cells in combination 

 or built up into a fabric much as a wall is built of bricks, that is. into a 



401. Cellular Structure or Tissue. Suppose numerous cells like 

 those of Fig. l-')7 to be heaped up like a pile of cannon-balls, and as they 

 grew, to be compacted together while soft and yielding; they would flatten 

 where they touched, and each sphere, 

 being touched by twelve surrounding 

 ones would become twelve-sided. Fig. 

 438 would represent one of them. 

 Suppose the contiguous faces to be 

 united into one wall or partition be- 

 tween adjacent cavities, and a cellular 

 structure would be formed, like that 

 shown in Fig. 439. Roots, steins, leaves, 

 and the whole of phan- 

 erogamous plants are a 

 fabric of countless num- L 



Ji^^, / ilPJ 



439 



bers of such cells. No 



such cxaet regularity in 



size and shape is ever 



actually found; but a nearly truthful magnified view of a small portion of 



i slice of the flower-stalk of a Calla Lily (Fig. 440) shows a fairly corres- 



440 

 ponding structure ; except that, owing to the great air-spaces of the interior, 

 the fabric maybe likened rather to a stack of chimneys than to a solid 

 fabric. In young and partly transparent parts one may discern the cel- 

 lular structure by looking down directly on the surface, as of a form- 

 ing root. (Fig. 82, 441. 442). 



402. The substance of which cell-walls are mainly composed is called 

 Cellulose. It is essentially the same in the stem of a delicate leaf or 



petal and in the wood of an Oak, except that in the latter the walls arc 



Pio. 438. Diagram of a vegetable cell, such aa it would be it' when Bpherical it 

 were equally pressed by similar Burrounding cells in h heap. 

 Pio. 189. Meal construction of cellular tissue bo formed, in section. 

 Pio. 140. Magnified vietr of s portion <>f s transverse slice of stem of Calla 



Lily. The great spaces arc tubular .iir-eh;umels l.uilt up by the Cttlla. 



