ANATOMY OF UORRICHIA FRFTESOENS. 



309 



BORRICHIA FRUTESCENS (L.) DC. 



Leaves (fig. 4!») fleshy, almost 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 hairs (fig. 50), 1 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. 



Collenchyrna (hypodermal) in several layers above and below the 

 large mestome bundles (five in the midvein). 



Chlorenchyma consisting of very compact palisade, 2-layered on 

 both surfaces; pneumatic tissue none. 



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



FlG.49.— Borrichia frntescens— leaf 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 ',)$). 



Fig. 50.— Borrichia 

 fr u tescens — loaf- 

 hairs. Scale 240. 



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

 ness, at somewhat regular intervals displacing the palisade on the 

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

 rude) frequent just beneath these extensions. 



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

 tissue; reinforced on the leptome side by a strong group of very thick- 

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

 and its elements beautifully differentiated, the sieve tubes each with 



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. 



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

 to consist of rounded, usually bicellular papillae. 



