116 REPORT OF COMMISSIONER OF FISH AND FISHERIES. 



tetraspores lining the walls of immersed conceptacles, zonate, cruciate, 

 or irregularly placed j cystocarps unknown. 



A small genus, comprising half a dozen species, wliicli form tliin crusts on rocks and 

 stones both in salt and fresh water. The systematic position of the genus is doubtful, 

 and must remain so until the cystocarps are known. Since the tetraspores are borne 

 in special conceptacles, the genus has been placed by some writers with the Coral- 

 lincce, although the species are not strictly calcareous. By others it is placed with 

 the Sqaamariece. Antheridia are only known in H. rivularis, where they are said by 

 Borzi to be long cylindrical cells formed from the superficial cells of the thallus, each 

 cell containing a number of spherical antherozoids arranged one above another. 



H. ROSEAj Kutz. {H. rubra, Harv., Phyc. Brit., PI. 250 j Farlow, in 

 Report of U. S. Fish Comm. for 1871.) 



Fronds thin, closely adherent to the substratum, cells of nearly the 

 same size in all parts of the frond ; conceptacles numerous, completely 

 immersed, si)herical ; tetraspores either zonate or irregularly divided, 

 lining the walls of the conceptacles and mixed with filiform, slender 

 paraphyses. 



On stones and rocks near low- water mark. 



Everywhere common. 



One of our commonest species, which forms continuous thin crusts, often of consid- 

 erable extent, tinging the rocks with a pinkish or somewhat brownish color ; not 

 easily mistaken for any other alga on our coast, except possibly young forms of 

 Pctrocelis, which is, however, thicker, more velvety in appearance, and darker in color. 



Suborder NEMALIEJS. 



{Helminthocladiece, Agardh &, Harvey.) 

 Fronds more or less gelatinous or occasionally coated with a calca- 

 reous deposit, filamentous, branching, formed of an axial portion com- 

 posed of elongated longitudinal filaments, which give off short, corym- 

 bose, horizontal branches, which constitute the cortical portion j anthe- 

 ridia in tufts on the superficial cells ; cystocarps immersed in the frond, 

 borne on the peripheral filaments, composed of densely packed chains 

 of spores radiating from a central cell, either without any proper enve- 

 lope, or with a filamentous involucre or surrounded by a proper mem- 

 branous pericarp ; tetraspores ? 



A comparatively small suborder, comprising species whose fronds, except in color, 

 resemble the fronds of the Chordariew in the Thceosporece, since they consist of an axis 

 composed of longitudinal filaments and a cortex of short, much-branched horizontal 

 filaments. All our species are soft and somewhat gelatinous, but the species of Lia- 

 gora, which abound in the tropics and are found in Southern Europe and in this 

 country in Florida and California, have a more or less distinct coating of carbonate 

 of lime. The procarps and cystocarps in this suborder are very simple. There are a few 

 species belonging to the genus Batrachospermum which occur in fresh water. In that 

 genus the formation of the cystocarps is very simple. The trichogyne and trichoporo 

 are represented by a single large cell, constircted near the base. After fertilization 

 the chains of spores are formed directly from the part below the constriction. In 



