Bbtts. — Rosette Plants at Cass. 



269 



The vascular bundles are small, and are surrounded by a sheath of thin- 

 walled, colourless cells. The xylem consists of vessels round in section, 

 with thick walls, and of xylem parenchyma. The amount of phloem is 

 small. The leaf is much thicker in the midrib, where the vascular bundle 

 is accompanied by a mass of large, rounded, thin-walled, colourless cells. 

 There is a smaller amount of this colourless tissue with the other bundles. 



Petiole (fig. 28). — The petiole is thick and fleshy, being used for water- 

 storage. The upper epidermis consists of large cells in which the lateral 

 walls are thin, and the inner and outer thickened, but not so much as in the 

 leaf -lamina. A cuticle as in the leaf is present. Many of the epidermal 



CL t 



Fig. 25. — Brachycome Sinclairii. Transverse section of leaf ( X 230). a, ridged 

 cuticle ; b, thick epidermal wall ; c, palisade tissue ; d, spongy tissue ; 

 e, guard-cell ridge. 



Fig. 26. — Brachycome Sinclairii. Upper epidermis of leaf (x 230). 



Fig. 27. — Brachycome Sinclairii. Lower epidermis of leaf (x 230). 



cells contain chloroplasts, and near the centre of the petiole, above the 

 midrib, a few of them are produced into long, unicellular hairs which 

 contain protoplasm. At the margin of the petiole are found a few capitate 

 glandular hairs. The lower epidermis is similar to the upper, except 

 that it does not produce any hairs, and the cells are smaller and contain 

 more chloroplasts. There are stomata on the upper but not on the lower 

 surface. 



There are five vascular bundles— a large one at the centre, and four very 

 small ones. The bundle-sheath is not clearly marked off from the small- 

 celled parenchyma surrounding the bundle. The structure of the bundles 

 is the same as in the leaf. 



