83 ELEMENTAE Y TISS VES. 



where the cell walls are somewhat thickened, Vbe prtonary partition 

 between contiguous cells: The 'middle lamella or inter -cellular 

 substance, as it is sometimes called. This lamella is of much the 

 same chemical composition as the remaining cell walls of the tissue, 

 and undergoes modification with it. 



PREPARATION SECOND: ELLIPSOIDAL CELLS, from the root of any 

 herbaceous plant; those of the JIi/<t<-inth grown in water are easily 

 obtainable. 



For this study a longisectiou of a root should be prepared in 

 the manner directed for the previous study, or better, after the 

 directions on p. 21. 



OBSERVE: 1. Thin walled ellipsoid cells, beneath the epider- 

 mal layer, making up the main body of the root the cortex, and 

 extending to the central cylinder. 



2. The cells toward the apex of the root are more isodia- 

 metric. 



3. The cell contents, together with the general characters of 

 the cortical tissue. Bastiirs Bot., p. 152. 



PREPARATION THIRD: EPIDERMAL and IRREGULAR PARENCHYMA 

 cells from the leaf of SCARLET GERANIUM. 



Remove a portion of the epidermis of the lower surface of the 

 leaf. This may be done by raising it at a cut margin and stripping 

 it back. It will come away as a transparent membrane. Mount in 

 water with the external surface of the epidermis uppermost. 



OBSERVE: 1. The irregular outline of the colorless cj>i<l 

 cells. 



2. tftoniates, with elliptical openings, at intervals. 



3. Trichornes in various stages growing from the 



The elongated cylindrical cell or cells composing them; the globose 

 glands at the apex of some. (Fig. 25.) This illustrates the fact that 

 cell walls, when not acted on from without, will develop with curved 

 surfaces. Bastin's Bot., p. 15G. 



PREPARATON FOURTH: Make thin cross-sections of small por- 

 tions of leaves, hardened and partly bleached, in 50 per cent, alco- 

 hol. In these the chlorophyll bodies retain their form and some of 

 their color. The green tint imparted to the alcohol shows the read, 

 iness with which the chlorophyll pi</nt< >/f is extracted by its solv- 

 ents. While sectioning, the razor and the leaf must be kept sup- 



