18 



PSILOTALES 



[CH. 



Sw. (fig. 118) and P. complanatum Sw., flourishes in moist 

 tropical regions of both hemispheres, growing either on soil 

 rich in organic substances or as an epiphyte. Both genera 

 are considered to be more or less saprophytic. 



Fig. 118. Psilotum triquetrum (J natural size). 



A. Synangium. 



B. Sporophyll after removal of the synangium. (M.S.) 



Psilotum. The common tropical species P. triquetrum 

 (fig. 118) is characterised by an underground rhizome which 

 forms a confused mass of dark brown branches covered with 

 filamentous hairs as substitutes for roots and gives off erect 

 repeatedly forked aerial shoots. In P. complanatum^ the habit 



1 Baker (87) A. p. 30. 



