4 ! 8 BULLETIN OF THE BUREAU OF FISHERIES. 



KEY TO ORDERS 



o. Frond usually of relatively large size, multinucleate, without division into cells 



/. 3. SlPHONALES (p. 430). 



oo. Frond divided into cells b. 



b. Cells uninucleate, chromatophore usually single, disk or net-shaped i. ULOTRICHALES (p. 418). 



66. Cells multinucleate, chromatophore net-shaped, or of numerous small disks in a cell 



2. SlPHONOCLADIALES (p. 423). 



Order 1. Ulotrichales. 



Confervoidese. in part, De Toni, 1889. 



Confervoideae, in part. Wille. in Engler and Prantl, 1897. 



Simple or branched filaments, sometimes membranes, rarely in few-celled families; 

 cells uninucleate, rarely multinucleate; chromatophore usually single, band, disk, net," 

 or star shaped, generally with one or more pyrenoids. Marine and fresh water. 



KEY TO FAMILIES. 



Frond membranaceous, either flat or forming a tube ; i. ULVACE/E (p. 418). 



Frond filamentous, branching, or a few-celled family ; usually with hairs . . .2. CH^TOPHORACE^ (p. 422). 



Family 1. ULVACE& (Lamouroux) Rabenhorst. 



Membranaceous, plane, or tubular fronds; cells uninucleate, with disk-shaped 

 chromatophores and one pyrenoid; asexual propagation by four-ciliate zoospores (some- 

 times bicUiate ?) ; sexual reproduction by similar biciliate gametes. 



Near the base of the frond the cells may send down rhizoidal prolongations to the 

 substratum, often uniting to form a thickened stipe; otherwise than this there is no 

 specialization of cells. Zoospores or gametes may be formed in any cell of the frond 

 except the lowest cells. The zygospore formed by the fusion of two gametes, after a 

 short period of motility with four cilia, settles down, loses its cilia, surrounds itself by a 

 membrane, and develops immediately into a new plant, forming a filament or small sack 

 which soon changes into the characteristic form of the frond. 



About loo species, mostly marine, rarely in fresh water, mostly in the littoral zone 

 throughout the world from Arctic to Antarctic regions. 



KEY TO GENERA. 



Frond tubular or flattened; simple or branched i. Enteromorpha (p. 418). 



Frond flat, often forming extensive sheets 2. Ulva (p. 420). 



Genus i. Enteromorpha Link. 



Enteromorpha, Link, 1810, p. 5. 



Ulva enteromorpha, Farlow, 1882. p. 43. 



Frond originating in a single series of cells, which by repeated division form a 

 tubular frond (sometimes flattened) , the membrane of which consists of a single layer of 

 cells; in some of the simpler species the tubular stage is not reached, and the frond in the 

 adult state consists of two or a few series of cells, united without any interior space; 

 simple or branched ; cells often arranged in longitudinal series. All the cells of the frond, 

 except the lowest, capable of producing zoospores or gametes, which are discharged 

 through an opening in the cell wall. 



Frond always attached at first, later often free floating. The genus is connected 

 with Ulva by E. lima, in which the tube is compressed and the membranes united in the 

 middle part. 



