310 



THE PLANT COVERING OF OCRACOKE ISLAND. 



a companion cell and a band of four or five cribrile parenchyma 



cells. 1 



Leaf anatomy of salt-marsh species. 



Characters given under species of the "sand strand," page 



1 Borrichia arhorescens (compare Warming, Halofyt-Studier, p. 212) is a very- 

 similar but larger plant of the tropical American strand. It differs from B. frutes- 

 cens in the following particulars, the characters being taken from material col- 

 lected in South Florida and Porto Rico: 



Hairs much thicker-walled, entirely disappearing in old (more than 1 year 

 old?) leaves; stomata on both surfaces, with guard cells slightly prominent on the 

 ventral face, less numerous and with guard cells slightly sunken on the dorsal 

 face; epidermal cell walls, especially the outer, thick; palisade interrupted both 

 above and below by extensions of the water-storage tissue, which on the ventral 

 side ultimately disorganize and form large lacunes; hypodermal coUenchyma 

 occurring where the palisade is interrupted on the ventral side; coUenchyma 

 taking the place of stereome as supports of the veins, especially strong on the lep- 

 tome side. 



From Warming's description and figure of B. arhorescens my specimens showed 

 important differences: (1) The presence of hairs (elsewhere in the same paper 

 Warming mentions their occurrence in this species) ; (2) stomata with guard cells 

 slightly prominent on the ventral surface (Warming writes "stomata sunken""); 

 (3) coUenchyma present and strongly developed; (4) mestome bundles in three 

 planes (one according to Warming) , some small ones being situated near the upper 

 and the lower epidermis, while the midvein is central in the water-storage tissue. 



