332 



THE MICROSCOPE. 



To return to cell- development ; we found the cell chang- 

 ing in its outward form, the transparent membranous cell 

 wall becoming thickened, and spontaneous fissure taking 

 place; and thus is formed a series of connected cells 

 variously modified and arranged, according to the conditions 

 under which they are developed and the functions which 

 they are destined to exercise. The typical form, as we have 



b 



Fig. 173. — a, elementary cells ; b, branched cellular tissue. 



before observed, of the vegetable cell is spheroidal ; but 

 when developed under pressure within walls, or denser 



tissues, it takes other shapes ; 

 as the oblong, lobed, square, 

 prismatical, cylindrical, fusi- 

 form, muriform, stellate, fila- 

 mentous, &c. : and is then 

 termed Parenchyma, and the 

 cells woven together are called 

 cellular tissue. In pulpy fruits 

 the cells may be easily separated 

 one from the other : a thin trans- 

 verse section of a strawberry is 

 represented at fig. 188, No. 15 : 

 within the cells are smaller 

 cells, commonly known as the 

 pulp. Fig. 173, a, is the ele- 

 mentary form of oval cells or 



1, A transverse section of stem of vpc ,i P lp~ m^ino- on tn tnp fnr- 

 Equisetum, showing the hexago- vesicles, passing On 10 tlie IOr- 



nai shape of ceils. 2, a vertical niation of branched cellular 



section of elongated cell. ,. i -n i -i i 



tissue, o. Kemarkable speci- 

 mens of the filamentous tissue may be seen in fig. 188, 

 No. 19, the circular elongated cells from the Mushroom ; 

 only another and more closely connected growth of muce- 

 dinous fungi, commonly called mushroom spawn. 



Fig. 174. 



