CHAPTER XXXVI. 



GLEICHENIACEAE. 



THIS family is represented by about twenty living species, all of which 

 are referred by some systematists to the single genus Gleichenia, 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. 



FIG. 308. 



Gleichenia, S\v. Mertensia, Willd. Scheme of branching of the leaf in the four sections 

 of the genus. (After Diels, from Engler and Prantl, Nat. PJianzenfam.') 



Among these Ferns an upright shrubby axis is occasionally found (Stroma- 

 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 (Platyzoma\ The leaves are 

 occasionally simply pinnate (Stromatopteris, 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 Gleichenia has a dichotomous leaf, 1 

 the branching is always a monopodial pinnation ; the appearance of "forking" 

 is the consequence of the two pinnules below the circinate but temporarily 



1 Goebel, Organography, vol. ii., p. 319, footnote. 



