SEA WEEDS 389 



bear to one another. The following table will probably assist the 

 reader in the determination of the orders, but it must be remem- 

 bered that a microscope will often be necessary for the examination 

 of the spores and the minute structure of fronds. 



CLASSIFICATION OF SEA WEEDS 



A. Chlorospermeffl Green-spored weeds. Fronds usually grass- 



green, and filamentous or membranous. 



1. ConfervacecB Frond thread-like, composed of cylindrical 



cells placed end to end. Spores very minute, formed 

 within the cells. 



2. UlvacecB Frond grass-green or purple, flat or tubular. 



Spores minute, ciliated, formed in the cells of the frond. 



3. Siphonacece Frond a single, thread-like, branching cell, 



or a spongy mass of many such cells. 



B. Kliodospermese Eed-spored weeds. Spores in globular con- 



ceptacles. Tetraspores (four-clustered spores) in globular 

 or cylindrical cells. Frond red, reddish brown, or purple. 



4. Ceramiacece Frond thread-like, jointed, one-siphoned, and 



more or less covered with a layer of cortical cells. Spores 

 grouped in transparent, membranous sacs, sometimes 

 surrounded by a whorl of short branchlets. 



5. SpyridiacecR Frond thread-like, jointed, one-siphoned, 



more or less covered with small cells. Spores formed 

 in the upper cells of branched, jointed, radiating threads, 

 enclosed in a cellular membrane in external concep- 

 tacles. 



6. CryptonemiacecB Frond more or less cartilaginous, com- 



posed of numerous jointed threads compacted by gela- 

 tine. Spores grouped without order in internal cells or 

 in external conceptacles. 



7. Rhodymeniacece Frond inarticulate, membranaceous, com- 



posed of polygonal cells, the surface cells forming a 

 continuous layer. Spores in beaded threads in external 

 conceptacles. 



8. Wrangeliacece Frond inarticulate, thread-like, traversed 



by a jointed tubular axis. Spores formed in the ter- 

 minal cells of clustered, branching, naked threads. 



9. HelminthocladicB Frond cylindrical, gelatinous, composed 



of filaments imbedded in gelatine. Spores formed on 

 branching, radiating threads that are enclosed in the 

 frond without conceptacles. 



