102 DICTYOTACE^.— Haliseris. 



■ff Frond linear, dichotomous. 



V. DiCTYOTA. 



•j-f Frond undivided. 



VIII. PUNCTARIA. 



IX. SoEANTHEKA, Post. and Rupr. (I do not see how this differs from Punctaria.) 



*** Frond cylindrical, or bag-like. 

 f Branched. 



VI. Stilophoea. Sori wart-like, composed of spores and moniliform threads. 



VII. DiCTYOSiPHON. Spores either solitary and scattered, or collected into dot-like 



sori. 



f f Unhranched, bag-like. 



X. ASPEROCOCCUS. 



**** Frond pierced with round holes, lace-like. 



XI. Hydroclathrus. 



1. HALISERIS. Tozzetti. 



Boot coated with woolly hairs. Frond flat, linear, membranaceous, traversed by 

 a cartilaginous midrib. Spores collected in naked sori, disposed in longitudinal 

 lines at either side of the midrib, and rising from both surfaces of the membra- 

 nous frond. Paranemata forming groups separate from the sporiferous sori. 



This is the only genus in the Order in which the frond is traversed by a midrib ; 

 and one species {R. Areschougia, J. Ag.) is described as being nerveless. In most 

 species the membranous border of the frond tears with ease in an oblique direction 

 toward the midrib ; so that it is rare to find specimens of full size in which the 

 lower part of the fronds is not much jagged. The margin is either entire, or 

 minutely denticulate, and is sometimes thicker than the rest of the membrane. In 

 two species the midrib throws off lateral secondary nerves which traverse the 

 frond toward the margin, ascending obliquely. Of the ten species known, four are 

 American, four South African, one Australian and Indian, and one a native of the 

 tropical and temperate regions of the Eastern Hemisphere. The name, derived 

 dXs and a-epis, is spelled Halyseris by Agardh, &c. 



