cells which are arranged in stellate clusters, adjoined to form com- 

 pound colonies by gelatinous strands.) Characium, which is much 

 more common, has spindle-shaped or ovoid cells growing on other 

 algae, on submerged aquatic plants, or on microfauna. There are 

 1 or more parietal chloroplasts, each with a pyrenoid (sometimes 

 several). The cells are mostly uninucleate. Biflagellate zoospores, 

 formed 2-128 in a cell, escape through an apical or lateral pore. 



CHARACIUM A. Braun in Kuetzing 1849, p. 208 



See characteristics as described for the family; cells variously 

 shaped, ovoid, fusiform, or cylindric, attached to a substrate (sub- 

 merged plants, larger algae, microfauna) by a stipe (usually) and 

 often with a basal attaching disc; rarely sessile; chloroplasts 1 or 

 several parietal plates which sometimes become diffuse; pyrenoids 

 1 to several, although rarely there are none; food reserve in the form 

 of starch. 



Key to the Species 



1. Cells epizoic on Crustacea, often specific as to host 2 



1. Cells epiphytic on miscellaneous plants but especially 



on filamentous algae 5 



2. Cells roimded at the apex 3. 



2. Cells narrowed to a spine at the apex 4 



3. Cells broadly ovoid or pyriform, on a short stout stalk._ C. Debaryanum 



3. Cells elongate-ellipsoid or narrowly obovoid C Hookeri 



4. Cells fusiform or slightly crescent-shaped, on a long, needle-like 



stipe without a holdfast at the base C limneticum 



4. Cells elongate-cyUndric, from a stipe which has a 



forked rhizoidal holdfast C. gracilipes 



5. Cells broadly pyriform or broadly ovate, or ovoid 6 



5. Cells narrowly ovoid, fusiform, lanceolate, falcate or cylindrical 8 



6. With a very slender stipe, 1 to IJ2 times as long 



as the cell body _.._ C. stipitatum 



6. With a stout stipe, much shorter than the length of the cell body- — 7 



7. Cells broadly ovate, 10-12/i wide - C. obtusum 



7. Cells pyriform, 13-15^1 wide. - C. operculum 



8. Cells elongate-fusiform, narrowed anteriorly but 



bluntly rounded at the tip - C. Rabenhorstii 



8. Cells lanceolate, falcate, or cylindric, ending in 



an apiculation or spine - 9 



9. Stipe enlarged at the base to form an attaching disc -- 10 



9. Stipe without a basal attaching disc — 12 



10. Cells straight, erect, the stipe short C. Pringsheimii 



10. Cells strongly curved or falcate 11 



11. Cells lanceolate or falcate - - - C. rostratum 



11. Cells broadly and imsymmetrically ellipsoid, convex on one 



margin, nearly straight on the other.. -C. ornithocephalum 



[215] 



