THE EPIDERMAL TISSUE. 



89 



The stomata of Marchantia may shortly be mentioned here in connexion with what 

 has already been said on Fig. 65. After the formation of the air-cavities which are 

 filled with outgrowths containing chlorophyll, one cell of the epidermis lying above the 



Fin. 76. — Supcrticial view of the stoma of Aneifniafraxitn- 

 folia: \s\\.\\ the epiderniis-cclls surroun<ling it; e epidermis, 

 jj gfuard-cells. 



Ml,. 77.— Transverse section through the leaf of 

 Pinns Pinaster (XSoo) ; j guard-cells of the stoma; 

 / its pore ; v entrance ; / air-cavity ; c cuticular- 

 ised layers of the epidermis ; a middle lamella, 

 I inner thickening layers of the cells beneath the 

 epidermis; g parenchyma of the leaf containing 

 clilorophyll. 



centre is divided by several bipartitions into four, six (Marchantia, Fegatclla) or several 

 (Rebouillia) cells, which are arranged radially about a point where their walls unite; 

 here the cells separate from one another, and the pore (/>o) originates surrounded by 

 four, six, or more guard-cells (Fig. 78, 5 and C, j/). Each of these cells is finally divided 



Fig. n%.— Marchantia polymorpha. Part of a young receptacle ; A vertical section, o epidermis, 5 partition-wall 

 between the air-cavities with their chlorophyll-cells chl; ^ large parenchyma-cell; j/ stoma; B and C young 

 stomata seen from above (X5So). 



by walls parallel to the epidermis-cell into 4-8 cells lying one above another, and the 

 stoma becomes a channel surrounded by 4-8 or more rows of cells. 



