282 



MANUAL OF BOTANY 



Fig. 612. 



conteDts, consisting of the protoplasm and various bodies em- 

 bedded in it or surrounded by it (figs. 612-614). The proto- 

 plasm, being the essential part, may iirst be examined. 



The Peotoplasm. — In the young slate of the cell the proto- 

 plasm fills it, and appears as a nearly transparent jelly-like 

 material, somewhat granular in cha- 

 racter, and saturated with water. 

 This condition is only transitory. 

 Very soon, in consequence of con- 

 tinual absorption of water, the cell, 

 kept turgid and stretched by the in- 

 ternal pressure, increases in size, and 

 the protoplasm does not keep pace in 

 its growth with the enlargement ; the 

 water accumulates in drops, which 

 gradually become larger, so that cavities 

 appear in the substance of the proto- 

 plasm, which soon fuse together, form- 

 ing one or more vacuoles filled with a 

 fluid called the cell-sap- ^^ such cells 

 the protoplasm often forms only a 

 lining to the cell-wall, the centre of 

 the cell being occupied by a single 

 large vacuole (fig. 612). The proto- 

 plasm thus lining the cell has been 

 called the primordial utricle. 



In the substance of the protoplasm, 

 whether filling the cell or not, there 



/■'/;/. 612. Cells from the root 

 of Fritillaria imperialis. 

 h. Cell-wall. k'. Nucleus. 

 *, k. Nucleus with nucleoli. 

 p. Primordial utricle, p', p' 

 Protoplasmic threade. s, s. 

 Cell-sap cavity. s\ 

 Vacuoles. After Saoh.-i. 



Fig. 613. 



Fkj. 61 :^. Vegetable cells. A. Very young. B. A little older, showing com- 

 mencing foniiatiou of vacuole, p. Protoplasm, n. Nucleus, r. A vacuole. 



exists somewhere a specially differentiated portion called the 

 nucleus (fig. 612, 7,), and frequently other less differentiated 



