90 Trigonantlieae 



cleveloped plants of the tribe. Tliey aboimd throughout the tropics and 

 the southern hemisphere, nor are they absent from the northern. In 

 Bazzania every known species is dioicous, and they are as numerous and 

 almost as difficult to define as those of Rubiis among phanerogams. Of 

 the fine genus Microjjtenjgium, whose complicate leaves, broadly winged 

 at the keel, are in some sort analagous to those of Fissidens among 

 mosses, I found an aberrant member, which may either rank as a sub- 

 genus, or better perhaps as a distinct genus. Instead of the pinnately- 

 branched stems, the unequally-bilobed leaves, the constantly-present 

 underleaves, and the trigonous '^exio.nth.oi ^licropterygium, we have here 

 very flat and frond-like stems with few branches, sx^ringing fi'om the 

 underside as in Cephaluzia; leaves so equally and closely comphcate that 

 they resemble in miniature a slightly-gaping bivalve shell, such as that 

 of the mussel (whence my name, Mytilopsis); underleaves entirely 

 wanting; perianths usually 4-angled below and 8-plicate at the apex. I 

 add a description of this curious and beautiful plant. 



^lYTILOPSIS nov. gen. 



CaudexhiQxi^ prostratus subclivisus rhizomatosus, caitles 

 lineari-froncliformes suberectos arcuantes, subsimplices vel 

 paiicirameos edens, ramis omnibus liypogenis s. posticis, 

 aliis flagellaribus. Folia perfecte plano-clisticlia compli- 

 cato-carinata subsequivalvia, margine panim hiantia, basi 

 transversa amplexicaulia, valvulis lamellisve ad apicem 

 usque accretis, carina superne angustissime alata; cellulce 

 praeminutae incrassatse verruculosae. Foliola caulina om- 

 nino nulla. Flores dioici cladogeni: ^^ amentiformes ; 

 hractecB monandise. BractecE floris o 2 — 3-jug8e tristichse, 

 intimae foliis sublongiores, tenuissimge, laxe areolatse, 

 ovatie obtuse complicato-concavae bifida^ subciliat^. Peri- 

 anthium liberum elongatum leptoderme,inferne 4-(rarius 3-) 

 angulum, apice 6- 7- vel 8-plicatum, ore longiciliatum. Ca- 

 lyptra ovalis tenuis. Capsula oblongo-cylindrica bistrata, 

 cellulis internis fibra semiannulari carentibus. Elateres 



