CELLULAR TISSUE. 



and constitutes the basis of vegetable tissues. The chemical formula 

 representing it is C 24 H 21 O 21 , or 2 (C 12 H 10 O 10 ) + HO.* It is allied 

 to starch, becomes yellow on the addition of iodine, and when acted 

 upon by iodine and sulphuric acid assumes a blue colour. The mem- 

 brane formed by it is permeable by fluids, and becomes altered in the 

 progress of growth, so as to acquire various degrees of consistence. In 

 the advanced stages of growth, plants consist of two kinds of tissue, 

 Cellular and Vascular, which, under various modifications, constitute 

 their Elementary organs. These, by their union, form the Compound 

 organs, by which the different functions of plants are carried on. 

 3. The elementary organs consist of vesicles and tubes, varying in 

 /-WW, form and size, and united in different ways. The vesicles 

 \Jl are cavities surrounded by a membrane, their length not 

 much exceeding their breadth (fig. 1) ; while the tubes are 

 similar cavities more or less elongated (figs. 3, 4). 



SECTION I. CELLULAR TISSUE. 

 1. FORM AND ARRANGEMENT OF CELLS. 



4. Cellular Tissue- is formed by the union of minute vesicles or blad- 

 ders, called cells, cellules, or 'utricles. This tissue is often called Parenchyma 

 (TT, beside or between, and #tYa, any thing effused or 

 spread out, tissue). The derivation of Parenchyma is, by some 

 given waj, through, and fy^ea, I infuse. The individual 

 cells of which it is composed, when allowed to develop them- 

 selves equally in all parts of their circumference, are usually 

 of a more or less rounded form (fig. 5, 6, 7) ; but, when 

 pressed upon during the progress of development, they be- 

 come more elongated in one direction than in another (fig. 2), 

 and often assume angular or polyhedral forms (fig. 8). 



234 



5. The following names have been applied by Morren, and other 

 authors, to the tissue made up of variously-formed cells: 1. Paren- 

 chyma, a general name for cellular tissue, but often applied to that 

 consisting of dodecahedral cells (fig. 8, 12, 13), which, when cut in 



* For the meaning of these and other chemical symbols, see Chap. II. Sect. I. Div. 2, on the 

 Food of Plants. Figs. 1, 5, 6, 7, 8. Cells, vesicles, or utricles, separate and combined. 



Fig. 2. Fusiform or spindle-shaped cell. Figs. 3, 4. Tubes or vessels. 



