Betts. — Rosette Plants at Cass. 



265 



hair are large, about twice as long as broad, and the apical cell is wedge- 

 shaped ; these cells are thick-walled throughout, but are not cuticularized ; 

 they contain protoplasm in the form of primordial utricle and protoplasmic 

 strands, and the nucleus is large and oval. The average length of hair is 

 0-5 mm. The upper epidermal cells are large, with slightly thickened 

 walls, and somewhat irregular in outline (fig. 20). Stomata are numerous 

 (about 155 per square millimetre) ; the guard-cells have thickened walls, 

 are protected by fairly prominent guard-cell ridges, and are at the same 

 level as the epidermis. 



Fig. 19. — Plantago triandra. Transverse section of leaf ( x 230). a, hair ; 

 b, basal cell of hair ; c, stoma ; d,' palisade parenchyma ; 

 e, spongy parenchyma ; /, hydathode. 



The lower epidermis is similar to the upper, except that the cells are 

 a little longer, but are smaller in section, and stomata are more numerous 

 (about 200 per square millimetre). A very thin cuticle is present on both 

 surfaces. In addition to the hairs described for the upper surface there 

 are hydathodes — sparingly developed on the upper but more numerous 



