INTRODUCTION TO CRYPTOGAMIC BOTANY. 529 



connected veins. The sporangia occupy both surfaces of the 

 fertile frond, the lobes of which are linear, entire, or pinnatifid. 

 In Acrostichum the fronds are coriaceous, the venation is 

 reticulate, and the sporangia are widely diffused, but confined 

 to the under side. Platy cerium has thick, spongy fronds, 

 widening upwards, shaped more or less like the horns of elks, 

 arising from imbricated orbicular or subcordate sterile fronds, 

 sometimes depressed, sometimes ascending. The veins, more- 

 over, of the fertile fronds run down to a stemlike base, different 

 from anything in the whole order. The sporangia occur in 

 patches, mixed with stellate scales, anticipating those of Nijjho- 

 bolus. Specimens are often seen in collections, growing against 

 a wall, or attached to a piece of board. Campium has the 

 interstices of the costte traversed by arcuate veins like Menis- 

 cium. In Poecilopteris there are strong costasform veins, con- 

 nected by network. In Gymnopteris the primary veinlets 

 divide the interstices of the veins into parallelogram ic arese, 

 which are themselves reticulate. The species of this tribe are, 

 with few exceptions, tropical or subtropical. It has not one 

 representative even in New Zealand. 



6. TiENiTiDEiE, Presl. 



Sori naked, linear, continuous, or rarely interrupted, seated 

 upon the veins or veinlets, from whence they extend to the 

 neighbouring parenchym. 



597. This tribe is very near to Acrostichacece, but differs 

 because the sori do not cover the surface indiscriminately, 

 though they run out in a narrow line over the parenchym, 

 which latter circumstance distinguishes them from Orcmivini- 

 tacece and Polypodiacece. Tcenitis* and Notholcena are the 

 best-known genera. In the former the veins are reticulate, 

 and the sorus parallel with the margin, but at a distance from 

 it. In the latter the sorus is marginal, but the veins forked 

 or pinnate. The under side of the fronds in this genus is 

 sometimes covered with white farinaceous powder. Manv 

 species are densely tomentose or squamose, circumstances 

 which bring them near to Gymnogramma, while othei- 



* Tcenitis is now, however, coutiucJ to about two species. 



34 



