306 



Transactions. 



The clilorenchyma is not differentiated into spongy and palisade tissue. 

 It consists of closely packed polygonal or roundish cells which contain 

 numerous chloroplasts. There are no intercellular air-spaces. 



Stomata are found on the lower surface only. The guard-cells are 

 sunken below the surface of the epidermis, and the stomata are further 

 protected by small guard-cell ridges over the opening. Subsidiary cells 

 are present. 



Fig. 36. — Astelia montana. Transverse section through midrib ( x 175). a, tomentum ; 

 b, upper epidermis ; c, aqueous tissue ; d, mesophyll ; e, stoma ; /, hair ; 

 g, stereome. 



The vascular bundle is surrounded by a large mass of sclerenchyma : 

 these cells are irregular and very closely packed, and have fairly thick cell- 

 walls. The xylem and the phloem have the cell-walls of all the paren- 

 chymatous cells lignified. The layer of mesophyll cells adjacent to the 

 sclerenchyma is devoid of chloroplasts. 



