CHAPTER ARXVL 
GLEICHENIACEAE. 
Tus family is represented by about twenty living species, all of which 
are referred by some systematists to the single genus Glecchenia, though 
others separate off the monotypic genera, Platyzoma, Br., and Stromatopteris, 
Mett. The living species are distributed throughout the tropics, whence they 
extend far southwards, but only in less degree north, and they are absent from 
the northern temperate zone. 
laaneenl 
Fic. 308. 
Gleichenia, Sw. § Mertensia, Willd. Scheme of branching of the leaf in the four sections 
of the genus. (After Diels, from Engler and Prantl, Nat. Pfanzenfam.) 
Among these Ferns an upright shrubby axis is occasionally found (S¢voma- 
topteris), but usually there is a creeping rhizome. which sometimes takes an 
ascending position. Upon it the leaves are solitary, often with long inter- 
nodes, but sometimes more closely arranged (P/atyzoma). The leaves are 
occasionally simply pinnate (S¢vomatopteris, Platyzoma); but usually they 
show higher degrees of branching, together with a peculiar straggling habit. 
The branching of the leaf has frequently been described as dichotomous ; 
but according to Goebel no species of Géerchenia has a dichotomous leaf,! 
the branching is always a monopodial pinnation ; the appearance of ‘‘forking” 
is the consequence of the two pinnules below the circinate but temporarily 
1Goebel, Organography, vol. ii., p. 319, footnote. 
