CELLULAR TISSUE. 



33 



35. Elongating and Ramifying Cells, This onward growth may 

 take place, moreover, without the formation of partitions at all ; 

 when elongated, vegetating cells 



are produced, whether simple or 

 branched. The hair-like bodies 

 that copiously appear on the sur- 

 face of young rootlets furnish ex- 

 amples of the kind, as is shown in 

 Fig. 13, 14. More conspicuous 

 examples are furnished by certain 

 Alga3 of the simplest structure, 

 where the cell grows out into a 

 tube of uninterrupted calibre, or 

 branches as it grows into a series 

 of such tubes with the cavity per- 

 fectly continuous throughout ; as 

 in Botrydium (Fig. 67-70), where an originally spherical cell is 

 extended and ramified below in the fashion of a root ; in Vauche- 

 ria (Fig. 71), where a slender tube forks or branches sparingly; 

 and in Bryopsis (Fig. 73), where numerous branches are very 



regularly produced. In these 

 cases, the fully developed plant, 



\\ A ^?R &m&\f=^ with a11 its bmnches ' is onl y one 



4 proliferous cell, extended from 



various points by this faculty 

 of continuous budding growth. 

 The mycelium or spawn of 

 Mushrooms, and the intricate 

 threads of Moulds (Fig. 74-76) are formed of very attenuated 

 branching cells. And in Lichens, cells of the same kind are 

 densely interwoven into a filamentous tissue (Fig. 15). 



36. Circulation in young Cells, A kind of circulation or move- 

 ment of rotation has been observed in numerous cells, particularly 

 in those that form the hairs of many plants, which are well situated 

 for observation ; and it probably takes place in most cells at an 

 early period, while yet filled with fluid. The string of bead-like 



FIG. 13. Magnified cellular tissue from the rootlet of a seedling Maple; some of the ex- 

 ternal cells growing out into root-hairs. 14. A few of the cells more highly magnified. 



FIG. 15. Entangled, filamentous, branching cells from the fibrous tissue of the Reindeer 

 Lichen (Cladonia rangiferina), magnified. 



