182 WISCONSIN PHYTOPLANKTON 



Order SIPHONOCLADIALES. 



Cells multinucleate, generally cylindrical and united to form simple 

 or branched thalli that are, at times, quite complicated in structure. 

 Chloroplasts disciform, parietal and numerous, or united by strands 

 to form a single reticulate structure. Pyrenoids generally present. 



Asexual reproduction by zoospores and aplanospores. 



Sexual reproduction isogamous by means of zoogametes; or heter- 

 ogamous by large non-motile oospheres and small motile antherozoids. 



The order is largely marine and only one representative, Cladophora, 

 has been found in the plankton. 



Family CLADOPHORACEAE. 



Filaments generally sessile, simple or branched, with septations be- 

 tween the cells complete. Walls of cells generally heavy, homogeneous 

 or lamellose, without a gelatinous envelope. Cells with numerous 

 parietal disciform chloroplasts or a single reticulate chloroplast ; multi- 

 nucleate ; with a single large central vaeuole. 



Asexual reproduction by zoospores and akinetes. 



Sexual reproduction isogamous, by means of zoogametes. 



CLADOPHORA Kiitzing 1843. 



Filaments branched, with the component cells in a single linear series ; 

 lateral branches arising at distal part of main branch cells and gener- 

 ally with an abundantly developed system of branching. Growth of 

 filaments confined to the apical region. Cells cylindrical, several times 

 as long as broad; multinucleate; with numerous parietal disciform 

 chloroplasts or the chloroplasts united by processes to form a single 

 reticulate chloroplast; pyrenoids numerous. 



Asexual reproduction by the formation of many biciliate zoospores in 

 any cell of the filament. 



Sexual reproduction isogamous, by means of biciliate zoogametes. 



CLADOPHORA GLOMERATA (L.) Kiitzing. PL 50, Figs. 1-3. 



Phycol. gener. 266. 1843; Collins, Tufts Coll. Studies 2: 360, pi. 13, fig. 124. 

 1909. 



Branching of filaments fairly dense in lower portion and very dense 

 at the apex. Ultimate branchlets containing several cells, straight or 

 slightly incurved, with ends rounded but not markedly attenuated. 

 Cells of main branches 6-7 times as long as broad, 3-6 times as broad 



