CELLULAR TISSUE, 



23 



and fruit appear to ordinary inspection to be formed of smaller parts, 

 which are themselves capable of division into still smaller portions. 

 Of what are these composed ? 



18. Cellular Structure. To obtain an answer to this question, we 

 examine, by the aid of a microscope, thin slices or sections of any 

 of these parts, such, for example, as the young rootlet of a seed- 

 ling plant. A magnified view of such a rootlet, as in Fig. 1, pre- 

 sents on the cross-section the appearance of a network, the meshes 

 of which divide the whole space into more or less regular cavi- 

 ties. A part of the transverse slice more highly magnified (Fig. 2) 

 shows the structure with greater distinctness. A perpendicular 

 slice (Fig. 3) exhibits somewhat similar meshes, showing that the 

 cavities do not run lengthwise through the whole root without in- 

 terruption. In whatever direction the sections are made, the cav- 

 ities are seen to be equally circumscribed, although the outlines 

 may vary in shape. Hence, we arrive at the conclusion, that the 

 fabric, or tissue, consists of a multitude of separate cavities, with 



closed partitions ; forming a structure not unlike a honeycomb. 

 This is also shown by the fact, that the liquid contained in a juicy 

 fruit, such as a grape or currant, does not escape when it is cut in 

 two. The cavities being called Cells, the tissue thus constructed 

 is termed Cellular Tissue. When the body is sufficiently trans- 

 lucent to be examined under the microscope by transmitted light, 

 this structure may usually be discerned without making a section. 



FIG. 1. Portion of a young root, magnified. 2 A transverse slice of the same, more mag- 

 nified 3 A smaller vertical slice, magnified. 



FIG. i Cellular tissue from the apple, as seen in a section. 5. Some of the detached cells 

 from the ripe fruit, magnified. 



FIG 6 Portion of a hair from the filament of the Spider Lily (Tradescantia), magnified: 

 o, vestige of the nucleus. 



