506 BULLETIN OF THE BUREAU OF FISHERIES. 



The genus is distinguished from Polysiphonia by the persistent trichoblasts and the 

 consequent characteristic habit. It is distinguished from Dasya by its monopodial 

 growth. 

 Brongniartella mucronata (Harvey) Schmitz. PI. CIX, fig. 4. 



Dasya mucronata, Harvey, 1853, p. 63. 

 Brongniartella mucronata, Schmitz, 18933, p. 218. 

 Brongniartella mucronata, De Toni, 1903, p. 1012. 

 A. A. B. Ex. No. 2 (Dasya mucronata). 

 P. B.-A. No. 247 (Dasya mucronata). 



Fronds robust, rather terete, 3 to 20 cm. tall, about 0.5 to i mm. in diameter in main stems, one or 

 more arising from a basal, disklike expansion, branching usually lateral and distant, sometimes dicho- 

 tomous, Igwer portions of the main stem and larger branches naked,. smaller branches and apical por- 

 tions of larger ones densely covered by monosiphonous, dichotomous, rather rigid, spreading trichoblasts 

 going out on all sides from the cortical layer and mucronate at the apices; peri central cells five, seg- 

 ments not conspicuous, about 0.5 diameter long in the main stem and larger branches, 1.5 to 2 diam- 

 eters in smaller branches, covered throughout by a dense cortex; tetrasporangia in somewhat spiral row 

 among the cortical cells of scarcely altered branchlets; antheridia and cystocarps unknown; texture 

 firm, cartilaginous; color of the stem and branches dull, brownish-red, that of the trichoblasts usually 

 brighter, rosy red. 



Florida and West Indies. 



Occasional on Bogue Beach, Beaufort, N. C., summer and autumn, usually sterile, rarely tetra- 

 sporic, few specimens, 3 to 6 cm. tall, dredged on coral reef offshore, May, 1907, and July, 1915. 



This species is easily recognized. Neither the species nor the genus^ is known elsewhere on our 

 coast north of Florida. 



Genus 5. Bostrychia Montagne. 



Bostrychia, Montagne, 1838, p. 39. 



Frond usually creeping with erect branches, less often erect, more or less flattened, 

 sometimes apparently terete, branching usually distichous and alternate, sometimes 

 somewhat dichotomous or radial, longer branches bearing two lateral rows of short 

 branches, usually of limited growth, ultimate branchlets simple or branched, often 

 monosiphonous; structure cellular, with a circle of 4 to n pericentral cells, the number 

 often varying from base to apex, naked or sooner or later inclosed by one or more layers 

 of cortical cells, the segments sometimes becoming indistinct from the transverse and 

 longitudinal division of the pericentral cells, apical growth monopodial, apices often 

 monosiphonous, often bent or inrolled, apical cell alternately transversely and obliquely 

 divided; tetrasporangia occurring in ultimate, more or less transformed, stichidiumlike , 

 branchlets, arising in whorls of 4 to 6 from the pericentral cells, triangularly divided, 

 more or less covered by a layer of small cover cells ; antheridia composed of a larger or 

 smaller number of the middle, thickened segments of simple, cylindrical branchlets, the 

 spermatangia occurring in a dense layer over the surface; procarps numerous in single 

 or double rows, embedded in the cortex of slightly thickened branchlets; cystocarps 

 broad-ovate, conspicuous, usually occurring singly, apparently at the apices of branch- 

 lets, pericarp fairly thin, opening by a conspicuous terminal carpostome, gonimoblast 

 composed of compressed or more elongated dichotomous-fastigiate filaments, forming 

 single long pear-shaped or club-shaped carpospores from their terminal segments. 



About 30 species, mostly in warm regions, usually in brackish water at the mouths 

 of rivers, often extending into fresh water, some species known only in fresh water. 



