CELLULAR TISSUE. 



Sectioni I. — Oellulae Tissue. 

 1. — Form and Arrangement of Cells. 



Celiulae Tissue is formed by the union of minute vesicles or 

 bladders, called cells, cellules, or utricles. This tissue is often called 

 Parenchyma {'Tta.^d, through, and lyyyiJja, an infusion). The terms 

 Parenchymatous, Areolar, Utricular, and Vesicular, when 

 1 applied to vegetable tissues, may be considered as synony- 



mous. The individual cells of which this tissue is com- 

 posed, when allowed to develop equally in all directions, 

 are usually of a more or less rounded form (figs. 5, 6, 7) ; 

 but during the progress of development they frequently 

 become more elongated in one direction than in another 

 (fig. 2), and often assume angular or polyhedral forms 

 (%■ 8). 





Figs. 

 '2. 3. 4. 



Fig. 5. 



Fig. S. 



Fig. r. 



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 (figs. 8, 12, 13), which, when cut in 

 any direction, exhibit a hexagonal form (figs. 14, 15), and hence the 

 • tissue is sometimes called hexagonenchyma (i^dyavog, six-angled) ; it is . 





Fig. 9. 



Fig. 10. 



Fig. 11. 



Fig. 12. 



seen in the pith of the Elder, and in young palm stems. 2. Sphceren- 

 chyma {^(l(pa,7^a, a sphere), spheroidal cells (fig. 5). 3. Merenchyma 



Fig.. 2. Fusiform or spindle-shaped cell. 

 8, CeUs, or utricles, separate and combined, 

 the forma of cells. 



'igs. 3, 4. Tubes or vessels. Figs. 5, 6, 1 

 Figs. 9, 10, 11, 12, 13. Figures representing 



