Ill] 



PSILOPHYTON 



19 



and crowded, small chaffy scales or larger spine-like processes. 

 Tips of branches when young circinately coiled. Erect shoots 

 proceeding from a horizontal rhizome bearing rhizoids. Shoots 

 vascular, bearing stomata. Sporangial wall multi-layered, 

 sporangia borne on the finer terminations of some of the younger 

 macroscopically smooth shoots, singly or in pairs (Fig. 6, p. 21). 

 (2) P. robustius, Daws. 1 . Stems rather stout, bark smooth or 

 slightly furrowed without macroscopic emergences, branching 

 chiefly lateral or pseudo-dichotomous when terminal. Termina- 

 tions of branches bearing sporangia in clusters. 



Fig. 5. Psilophyton princeps, Dawson. Type speci- 

 mens (1859) with small scale-like emergences, two 

 of the specimens showing the circulate vernation. 

 After Dawson (1859). 



(3) P. elegans, Daws. 2 . Axes very slender, dichotomously 

 branched, produced in tufts from thin rhizomes. Surface smooth, 

 with very delicate wrinkles, but without macroscopic emergences. 

 Fructification (?) believed to consist of small oval bodies borne 

 below the bifurcations of the axes. 



More recently important observations have been published on 

 Psilophyton by Solms Laubach 3 , and David White 4 . The former 

 recognises P. princeps alone as a good species. Dawson's other 

 types of the same genus are regarded as indefinable. White 4 

 discriminates between a spiny type of Psilophyton (P. ornatum) 



1 Dawson (1871), PL XII. 



2 Dawson (1871), p. 40, PI. X, figs. 122, 123. 



3 Solms Laubach (1895), p. 76. 



4 White (1905), p. 61. 



2. 2 



