SMITHSONIAN MISCELLANEOUS COLLECTIONS 



VOL. 



61 



various forms are at any rate of the closest interrelation, that they are 

 similarly dimorphic, and that their sterile fronds at least are scarcely 

 distinguishable from each other. 



The sterile fronds of Trachypteris being entire, subspatulate, ex- 

 stipitate, and arranged in a rotate basal tuft are thus in shape, 

 structure, and habit very dissimilar from Saffordia, which they 

 resemble chiefly in venation and in the similarly dense paleaceous 

 covering of the under surface. The fertile fronds are slender and 

 very long-stipitate, the blades varying from ternately divided to 

 pinnatifid (with 4 to 7 segments) to fully pinnate, with 3 or 4 pairs 



of distant subsessile segments. 

 The basal segments may even 

 be lobed upon the proximal 

 side, the lobes more or less 

 produced (as shown in 

 Hooker's figure and in the 

 Bolivian specimen at hand) ; 

 and it is the basiscopic form 

 thus assumed which, together 

 with the ultimate venation and 

 the type of soriation, offers a 

 suggestion as to a possible 

 common origin of Trachyp- 

 teris and Saffordia. The most 

 notable differences between 

 the two genera lie in the ex- 

 treme dimorphism exhibited 

 by Trachypteris — the complete 

 restriction of vegetative and reproductive activities to separate leaves. 

 Thus, as might be expected, only the sterile fronds are persistent, the 

 fertile fronds shrivelling after maturity ; while in Saffordia the fertile 

 and sterile fronds are alike and are stout, rigidly erect and long-per- 

 sistent, characters consequent upon the parallel expression of both 

 vegetative and reproductive functions in the same frond. Nearly all 

 fronds of Saffordia are fertile and all are truly vegetative. 



With respect to soriation there is a strong similarity between 

 Trachypteris and t Saffordia, the difference being in extent rather than 

 in kind. The fertile fronds of Trachypteris have the sporangia nearly 

 covering the under surface of the segments, only the costal row of 

 areoles commonly being devoid of them ; and thus, because of the nar- 

 rowness of the segments, the two broad bands of sporangia nearly 



Fig. 1. — Blade of fertile frond of Tra- 

 chypteris from Bolivia {Williams 1177), 

 intermediate between the Brazil and Gal- 

 apagos forms. Natural size. 



