120 



RELATIONS OF MAN WITH EXTERNAL NATURE. 



or granular, mass, which always contains, when growing, some of the quinary 

 nitrogenous, albuminoid matter or protoplasm, absolutely essential to all vital 

 activity: the outer layer of this endoplast is rather firmer than the rest, and 

 has been named the primordial utricle; within, or upon, the endoplast is fre- 



Fig. 46. 



Fig. 46. Examples of vegetable cells (Schleiden, and others), a, conjoined and separate oval cells of the 

 yeast plant, torula cerevisiae; fc, cells of an algaceons plant, haemato-coccus binalis, single, double, and 

 clustered in fours ; c, polyhedral cells, with nuclei, nucleoli. clear contents, and distinct walls, from the 

 onion; d 1, polyhedral cell from the potato, containing a nucleus, and many starch -grains ; 2, a single 

 starch-grain more highly magnified, showing the concentrate strife; e, cells filled with concentric deposit 

 of ligneous matter, from the gritty part of a pear; /. stellate cells, from the pith of the rush, showing the 

 union of the different points of the cells, and the intercellular spaces. Moderately magnified. 



quently found, at least in growing cells, ft, c, d, a smaller vesicular body named 

 the nucleus, having in its interior one or two nucleoli, and constituting appar- 

 ently a special centre of activity or growth. The entire endoplast, thus de- 

 scribed, is the essential part of every vegetable cell. Outside the endoplast, is 

 the second elementary part, named the cell-wall or periplast, c, d, e, which is at 

 first, always thin, homogeneous, and transparent, and consists of the ternary 



Fig. 47. 



Fig. 47. Example of modifications of vegetable cells, forming the so-called vascular tissues of plants; 

 from the Italian reed (Schleiden). a, elongated polyhedral cells of the pith ; b. cells of the cuticle, containing 

 granules of chlorophyll; c, annular vessel, formed by the union of cells, and absorption of their intermediate 

 septa; rf, spiral vessel, formed by union of cells, and deposit of ligneous matter in spiral lines; e, dotted 

 vessel or dticf, formed by another mode of ligneous deposit within coalesced cells. To the right of this are 

 woody fibres,/, formed by solidification of fusiform cells with lignin. Moderately magnified. 



cellulose tissue ; its office is evidently protective and supporting, but it permits 

 of the passage of dissolved materials into and out of the endoplast which it 

 surrounds physical processes essential to nutrition and growth. The cell so 

 constituted may alter in size and shape, may coalesce with other cells, Fig. 

 47, a, may have its cell-wall perforated, c, or thickened by internal deposits, 

 dj e, or its contents may be altered in the most diverse ways. Again, it may 



