528 INTRODUCTION TO CRYPTOGAMIC BOTANY. 



greater or less latitude. Fe'e, however, iucludes the helicogy- 

 rate ferns also in the general denomination of Polypodiacew, 

 dividing them into twenty-six sections. Brongniart, on the 

 contrary, in his article on ferns, in Orbigny's Dictionary, who 

 adopts Polypodiacece as a tribe, divides it into nine sections, 

 Acrostichece, Tcenitideoe, Grammitidece, Polypodiacece, As- 

 pidiem, Aspleniece, Adiantece, Dicksoniece, and Woodsiew. 

 It is, in fact, of little consequence whether the divisions be 

 called tribes or subtribes, provided it be borne in mind that all 

 the divisions are not of equal value. However they may be 

 apportioned, the arrangement of authors, in most cases, is 

 essentially the same, though each authority may differ from 

 the others in some few particulars. 



596. I begin, then, with Acrostichacece, which differ from 

 all other ferns, in the sporangia occupying not merely the 

 veins of whatsoever order, but the perenchymal interstices 

 themselves. In Tcenitidece, indeed, the sori encroach upon 

 the parenchym, but merely by the junction of neighbouring 

 sori in a direct line. The fertile fronds are mostly different in 

 form and aspect from the sterile fronds, and are generally 

 more or less contracted, sometimes so much so as to suggest 

 the presence of an indusium, which, however, does not exist. 

 All the species were formerly included under Acrostichum, 

 which is now broken up into several genera, with more or less 

 propriety, from the venation of the sterile fronds (for that of 

 the contracted fertile fronds is often obscure), and other cha- 

 racters. Majjlioglossum, for instance, has simple oblong or 

 linear lanceolate leaves, with simple or forked veins, whose 

 tips are free and clavate. In Polyhotrya the tips of the 

 radiating or pinnate veins are free, and the sporangia occupy 

 one or both sides of the spikelike segments of the fertile fronds. 

 Stenochlcena is very nearly allied, and differs from Polyhotrya 

 in the petioles being articulated with the rachis. S. hetero- 

 morplia, like most of the species, climbs lofty trees by means 

 of the stout rhizoma. The fronds are very different in different 

 parts of the plant. This is the only species of the tribe which 

 occurs in New Zealand. Olfersia agrees with Polyhotrya in 

 the character of its fertile fronds, but differs in habit and the 



