4 BOTANY. 



(e) Mount carefully in pure water a piece (3 to 4 centimetres) of one 

 of tlie young " silks" of Indian corn. Tlie movement is well seen in 

 the long cells. Repeat tbe foregoing experiments. 



(/) The following may be taken also, viz. : the stamen hairs of 

 Spiderwort, the epidermis of Live-for-ever leaf, fresh specimens of 

 the Stoneworts (Chara and Nilella), Eelgrass, etc. 



7. The Plant-Cell.— In all commoii plants the protoplasm 

 is found in little masses of definite shapes, each one en" 

 closed in a little box (Fig. 1). The substance of these 

 boxes was made by the protoplasm, somewhat as the snail 

 makes its shell. Each mass of protoplasm with its box is 

 called a Plant-cell, and the sides of the box are called the 

 walls of the cell, or the cell-wall. 



8. The cell-wall is composed of carbon, hydrogen, and 

 oxygen (C^Hj^O^,), and has been named cellulose. At first 



Fig. 3. — Longitudinal section of a portion of the stem of Garden Balsam, v, 

 annular vessel; «', a vessel with thickenings which are partly spiral and partly 

 annular; v", v"', v"", several varieties of spiral vessels; v"'", a reticulated 

 vessel. 



it is very thin, but as the protoplasm grows older it thick- 

 ens its wall by continually adding new material to it, so 

 that at last it may be more than a hundred times as thick 

 as at the beginning. 



9. The cell- wall may be thickened uniformly, or, as more 

 frequently happens, some portions may be much more 

 thickened than others. When it is uniform the wall shows 



