INTRODUCTION TO CRYPTOGAMIC BOTANY. 547 



18. GleicheniacEjE, Kze. 



Sporangia sessile or subsessile, globose, subglobose, or trigo- 

 nal, surrounded by a complete ring ; bursting longitudinally. 

 Rhizoma creeping or climbing. 



623. The rampant, mostly divided, rhizoma and habit, rather 

 than any very definite characters, separate this little tribe from 

 the arboreous Gyatheacece. In all, the sporangia are few in 

 number, and disposed in a radiating manner, so that the 

 narrow end is internal They are often seated in a little cavity, 

 and are highly deciduous. The fronds are generally forked or 

 trifid, the third or middle division being supplied sometimes 

 by a little bulblike body. Flatyzoma has, however, simple 

 fronds, by which character it is principally distinguished. 

 Gleichenia has pinnate or forked free veins and veinlets, with 

 apical (Galymella, Presl) or immersed superficial sori. Mer- 

 tensia differs in its coarse habit and medial sori, with more 

 evident venation. Sticherus differs in its biserial sori. Presl 

 describes the venation as reticulate, but this is denied by Smith. 

 All are tropical or subtropical, with the exception of such as 

 affect the southern islands. Gleichenia has four species in 

 New Zealand. 



II. Ophioglossace^, Lindl, Hook, <&c. 

 Ophioglossb^, R. B. 

 Fronds entire or divided, straight in a3stivation ; fertile 

 fronds reduced to a linear strapshaped process, the edge of 

 which produces a single row of connate bivalvate sporangia. 



624. The asstivation of these plants is so different from that 

 of ferns, and the sporangia so unlike those of Marattiacew, 

 which can alone be compared with them, that in the absence 

 of all information as to the development of the spores, I cannot 

 but consider them as a distinct natural order. The sporangia, 

 in fact, are nothing more than mere sacs formed in the edge of 

 the fertile frond, and resemble rather those of Lycopods than 

 ferns. The order consists of four good genera, Ophioglossum, 

 BotrychiuTYi, Helminthostachys, and Rhizoglossuon. The 

 first has sometimes reticulate nervation, sometimes the fronds 

 are nearly nerveless. The greater part of the supposed species 



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