142 REPORT OF COMMISSIONER OF FISH AND FISHERIES. 



IS^EMASTOMA. 



(From VT^iia, a thread, and aro/na, a mouth.) 



Fronds gelatiuo-carnose, compressed -cylindrical or plane, diclioto- 

 mous or subpinnate, composed of an axial layer of densely woven longi- 

 tudinal filaments^ from whicli are given off short, lateral, dichotomous, 

 fastigiate filaments, which are united by a gelatinous substance to form 

 a peripheral layer j tetraspores cruciate, borne in the peripheral layer j 

 antheridia borne on the superficial cells of the perii)hery; cystocarps 

 (favellse) buried in the peripheral layer, spores escaping by a narrow 

 opening between the peripheral filaments. 



A genus comprising not far from a dozen species, which inhabit principally the 

 warmer waters of the globe, the genus being particularly well represented in Aus- 

 tralia. The fronds of the different species vary from only slightly compressed and 

 linear to broad and palmate, and in G. marginifera the frond resembles in shape that 

 of Bhodymenia imlmata. The substance is rather gelatinous and the microscopic struc- 

 ture resembles very closely that of the fronds of some of the NemaViece. The fruit of 

 N. marginifera is described by Bornet, in Notes Algologiques, as being a true favella like 

 that of CalUthamnion. The genus is generally placed near Gloiosiplionia, and, like that 

 genus, closely connects the Ceramiea? with the Crypionemece. 



2^. (?) Bairdii, Farlow, Proc. Am. Acad. Arts and Sciences, 1875, 

 p. 351. 



Fronds purplish-rose colored, gelatinous, four inches long, one inch 

 wide below, vermiform, once or twice dichotomously divided, axils acute, 

 apices attenuated j tetraspores cruciate, borne on the tips of the peri- 

 pheral filaments 5 cystocarps 



Washed ashore at Gay Head, IF. O. F. 



A very rare species, of which only a single specimen is known. It was found on the 

 beach near the light-house at Gay Head, Mass., in company with Scinaia furcellata, in 

 August, 1871. The specimen was a fragment, without the base of the plant, but 

 with abundant tetraspores, which were borne on the tips of the peripheral filaments. 

 In the absence of cystocarpic specimens the genus cannot be ascertained with cer- 

 tainty, and botanists who visit Gay Head, should seach for the plant by dredging off 

 the Devil's Bridge in tive to ten fathoms. The specimen collected was at first sup- 

 posed to be a portion of a broad specimen of Nemalion imrxmreum, a species not yet 

 known on our coast. The peripheral filaments are loosely united together by a gela- 

 tinous mass, as in the subgenus GymnoiMoea oi A.giiT(\h. 



Suborder DUMONTIE^. 



Fronds tubular, branching or proliferous j cystocarps immersed in 

 the frond, composed of a single mass of irregularly placed cells, similar 

 in most respects to those of the Cryptonemiecc. 



A small suborder, included by Harvey in the Cryptonemiew. The development of the 

 cystocarps is not well known, and on our coast there is no material to be obtained for 

 the study of the suborder. The common DiimonUa fil'iformis of Northern Europe is 

 wanting with us, and the genus Halosaccion, of which we have one representative, 



