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on the lower surface. They are of the capitate form (Haberlandt*). They 

 consist of two parts — (1) the basal portion or foot; (2) the head, of about 

 2 cells. The cells of this latter portion have thickened, non-cuticularized 

 walls (fig. 19). 



The chlorenchyma is differentiated. The palisade tissue consists of 1-3 

 rows of cells— large, broad cells, the outer layer being composed of cells 

 about twice as deep as broad, the inner layer or layers of cells about as 

 broad' as deep. The cells are thin- walled, fairly closely arranged, and 

 contain numerous small ellipsoidal chloroplasts. The spongy tissue also 

 consists of large, thin-walled, oval or somewhat irregular cells, containing 

 a smaller number of chloroplasts. The chloroplasts in the palisade tissue 

 are slightly larger than in the spongy tissue. Beneath each stoma there 

 is a fair-sized air-space. 



The vascular bundles are not numerous and are very small. In the 

 midrib there is, between the vascular bundle and the lower surface, a 

 small amount of aqueous tissue, consisting of rounded cells which are 



Fig. 20. — Plantago triandra. Upper epidermis of leaf ( x 230). 



a, guard- cells ; b, base of hair. 

 Fig. 21. — Plantago triandra. Jointed hair(x 48). 



either colourless or contain a few chloroplasts. The mesophyll above the 

 vascular bundle is not differentiated, and consists of very large cells which 

 contain chloroplasts. Below the midrib the cells of the lower epidermis 

 are much smaller, are circular in transverse section, and have all their 

 walls thickened. Above the lower epidermis, in the midrib, is a single 

 layer of colourless collenchyma. 



The vascular bundle of the midrib is small, and is surrounded by a 

 bundle-sheath of fairly large, thin-walled cells, in a few of which there is 

 a small number of chloroplasts. The xylem consists of vessels of small 

 diameter, together with xylem parenchyma. There is also parenchyma with 

 the phloem. Above the xylem and below the phloem there is a small amount 

 of sclerenchyma, consisting of small irregular cells with thick walls. 



* HABERLA.NDT, Physiologicul Plant Anatomy (English translation), p. 491 ; London, 

 1914. 



