208 BOTANICAL GAZETTE [MARCH 
of their cells is similar to that of many xerophilous mosses, hepatics, 
selaginellas, and ferns. The filmy ferns are not capable of enduring 
as complete a removal of water as are the other archegoniates men- 
tioned, but in view of the extremely hygrophilous character of 
most members of the family, it is sufficiently noteworthy that the 
few species which grow as high epiphytes in the Jamaican forests 
Fic. 8.—Diagram to show the maximum extent to which the sap cavities of the 
cells of Hymenophyllum polyanthos may be occupied by air bubbles in desiccated living 
leaves. 
are capable of enduring as great water loss as they are. Whereas 
several families of flowering plants have contributed to the Pr 
phytic flora of the rain forest species which are of xerophilous 
structure, the Hymenophyllaceae have contributed a small grouP 
of species the xerophily of which resides not at all in their struc 
ture, but in the capacity of the protoplasmic utricle to withstand 
the removal of the sap which is its source of water and nutrient 
salts. 
