568 Transactions. 



Epidermis on both upper and, lower sides has somewhat thickened 

 outer walls and cuticle. Some of the cells of the upper epidermis contain 

 anthocyan. Stomata are of medium size, or rather large, and equally 

 numerous on both surfaces. They are not sunk in the epidermis. The 

 guard-cells have conspicuous chlorophyll grains. 



Mesophyll : [a.) A single layer of rounded, closely packed cells, with 

 comparatively numerous chlorophyll grains. (&.) 2-3 layers of typical pali- 

 sade parenchyma, of very closely packed cells, (c.) 3-4 layers of large, 

 irregular cells, with small intercellular spaces and very few chromatophores. 

 {d.) 2 layers of smaller, rounded cells, with larger spaces, forming a kind of 

 reduced spongy parenchyma. 



The midrib has a well-marked endodermis, and an upper and lower band 

 of sclerenchyma. 



15. Cotula dioica. 

 Leaj. 



Epidermis has a thin cuticle, marked with deUcate striations. On both 

 surfaces are pits with glandular hairs. Each hair consists of 3-4 short basal 

 cells, with abundant dark contents, and a narrow terminal cell with clear 

 contents. The hairs are much longer on the lower surface than on the 

 upper, and not situated in such deep pits. Stomata are ecjually numerous 

 on both surfaces. They are large, with guard-cells containing very con- 

 spicuous large spherical chromatophores, found constantly arranged in a 

 definite way. lining the inner wall of the cell. 



Mesophyll : («.) 3 layers of irregular, somewhat short cells, with few, 

 but very large, ellipsoidal chromatophores. (6.) 4-5 layers of large poly- 

 gonal cells with few chromatophores, and few very small intercellular 

 spaces ; this probably functions as a water-bearing tissue, (c.) 2-3 layers 

 of cells, with chromatophores almost as numerous as in a ; this constitutes 

 a kind of spongy parenchyma of rounded cells, loosely arranged. The 

 lowest row is of smaller more regular cells. 



The midrib is fairly large, and has a mass of colourless small-celled 

 parenchyma above and below, though there is no distinct endodermis. The 

 xylem is very conspicuous, the vessels being arranged in parallel rows. 



16. Cotula coronopifolia. 

 Leaf (A, from Salt Meadows ; B, Submerged). 



A. — Epidermis has slightly thickened outer walls and cuticle. It is 

 marked with fine striations (c/. C. dioica). The stomata are equally nume- 

 Tous on either surface. They are not so large as those of C. dioica, and in 

 surface-view (fig. 16, d) are seen to be sUghtly overarched by neighbouring 

 epidermal cells. On both surfaces are pecuUar pointed multicellular glan- 

 dular hairs, recalling those of C. dioica, though they are not situated in 

 depressions. 



Mesophyll : {a.) 3 layers of rounded, closely packed, regular cells; with 

 large but iiot numerous chromatophores. (6.) 10-12 irregular layers of 

 rounded cells with few chlorophyll grains and large intercellular spaces, 

 (c.) A single layer of closely packed elUpsoidal cells, with chromatophores 

 as numerous as those in a. 



Midrib has a prominent sheath, well-marked xylem, and httle phloem, 

 embedded in sclerenchyma. There are 2 or 3 layers of colourless paren- 

 chymatous cells surrounding the midrib. 



