102 HISTOLOGICAL BOTANY. 



cells composing the soft flesh are formed of pure cellulose ; 

 but those of the cells composing the skin are so modified 

 that they are more extensible, highly elastic, and almost 

 impermeable to water, and those of the hard cells among 

 the veins are so converted that they are hard, inelastic, and 

 are easily penetrated by water without absorbing much. 

 When modified as in the skin, the cell-wall is said to be 

 Cuticularized ; and when modified as in the hard cells of 

 veins, it is said to be Lignified. 



Leaves of the Susuki (Miscanthus japonicus) and stems 

 of the Tokusa (Equisetum hyemale, var. japonicum) are 

 very hard from the deposition of the salts of silica in con- 

 siderable quantity in the cell-wall. In this case the cell- 

 wall is said to be Mineralized. 



All species of Gorallina (Coral-like Algae) and some of 

 Ghara become very hard from the deposition of the salts of 

 lime. 



The external cell-walls of the sea-weeds, as the Kombu 

 and Funori (Gloiopeltis coliformis), can absorb a large 

 quantity of water and become gelatinous ; such cell-walls 

 are said to be Mucilaginous. 



Modified cell-wall 



Cuticularized Cell-wall. 

 Lignified Cell-wall. 

 Mineralized Cell-wall. 

 Mucilaginous Cell-wall. 



2. THE PROTOPLASM. 



The Protoplasm consists of albuminous substances, 

 water, and a small proportion of ash-constituents. It is 

 usually a semifluid substance appearing more or less 

 granular from the presence of starch grains, oil-drops, etc. ; 

 but in a few cases it appears homogeneous. As the pro- 

 toplasm is the seat of all living functions it must contain 



