298 



Transactions. 



The spongy tissue consists of about 5 rows of large,- irregular cells which 

 have thin walls. There are fairly large air-spaces between the cells. The 

 cells of the layer jvist above the lower epidermis are much smaller. 



The Midrib. — -There are three vascular bundles in the midrib. The 

 lignified elements of the xylem are arranged regularly in rows which are 



Fig. 24. — Senecio bellidioides. Transverse section through midrib of leaf. 'Pa, multi- 

 cellular hair ; b, aqueous tissue ; c, xylem ; d, phloem ; e, canal lined by 

 epithelial layer ; /, chlorenchyma ; g, glandular hair. 



separated by xylem parenchyma. There is a good deal of parenchyma 

 with the phloem. Beneath the phloem of each bundle there are 1 or 2 

 large canals, which are lined by epithelial cells. 



