74 CELLULAR TEXTURE. - [l.ECT. III. 



are filled with the same green juice in leaves, which 

 are composed of a layer of cellular substance 

 placed betwixt two layers of cuticle. The medulla 

 or pith of plants is, also, composed of these cells, 

 filled, in young and succulent plants and branches, 

 with water, or watery fluids ; but in older plants, 

 and in the trunks and branches of trees, not succu- 

 lent, they are generally empty. In the latter the 

 shape and structure of the cells are most conspi- 

 cuous, and easily observed. Thus, if a transverse 

 or longitudinal section of a twig of Spanish Broom, 

 in the second year of the growth of the twig, be 

 placed under the microscope, or even a common 

 lens, the pith of it displays in the most beautiful 

 manner the hexagonal cells, the transparent iride- 

 scent appearance of the membrane forming their 

 walls, and the situation of the communicating pores. 

 It is well seen also by the aid of the microscope 

 in the pith of many other plants. The petals of 

 flowers are almost entirely composed of cellular 

 texture, the cells of which are filled with juices 

 fitted to refract and reflect the rays of light, so as 

 to produce the brilliant and delicate tints with 

 which the pencil of Nature has embellished these 

 parts. In the same manner it enters into the com- 

 position of the stamens, the stigma, and even the 

 pollen or fecundating farina of the flower. The 

 fleshy parts also of succulent roots, and of pulpy 

 fruits, are formed of this cellular texture tilled 



