ANATOMY OF BORRICHIA FRUTESCENS. 



309 



BORRICHIA FRUTESCENS (L.) DC'. 



Leaves (fig. 49) fleshy, jilniost vertical, imperfectly isolateral, the sur- 

 face glistening, whitish, mealy looking, especially in young leaves. 



Epidermis (fig. 49) with small, thin- walled cells, very many of 

 which are extended by tangential division into commonly 2 to 4 

 celled, thin- walled, pointed, usually bent haii's (fig. 50),' the whole 

 forming a very dense covering and giving the leaf its peculiar, glis- 

 tening aspect; stomata only on the ventral surface, the guard cells 

 slightly sunken. 



Collenchyma (hypodermal) in several layers abov(^ and l)elow the 

 large mestome bundles (five in the midvein). 



CJdorenchyma consisting of very compact palisade, 2-layered on 

 .both surfaces; pneumatic tissue none. 



Colorless parenchyma (water-storage tissue) (fig. 49) occupying the 



FiqA9 .—Borrichia frutescens—\ea,{ section. Trans- 

 verse section, showing epidermis of ventral sur- 

 face (Ep); palisade (P); colorless parenchyma 

 (C T); hadrome (H) and leptome (L) of a small 

 mestome bundle; and epidermis of dorsal surface 

 (ep). Scale 320. 



Pig. 50.— Borrichia 

 frutescens—leat- 

 hairs. Scale 340. 



interior of the leaf and forming rather more than one-half its thick- 

 ness, at somewhat regular intervals displacing the i>alisade on tlie 

 dorsal side and extending to the epidermis. Ducts (on the ventral 

 side) frequent just beneath these extensions. 



Mestome bundles of the veins (fig. 49) lying deep in the water-storage 

 tissue; reinforced on the leptome side b}' a strong group of very thick- 

 walled stereome, on the hadroine side by a smaller group; leptome 

 and its elements beautifully differentiated, the sieve tubes each witli 



water-storage tissue in the interior of the leaf and the absence of hairs— just the 

 converse of what one would expect as the differential characters between a dune 

 and a salt-marsh species. 



' The apical cells are easily broken off, so that in older leaves the covering appears 

 to consist of rounded, usually biceliular papillae. 



