Species of this genus are almost invariably confined to hard or 

 semi-hard water and in general are index organisms for high pH. 



Cladophora is a fairly large genus composed of many marine and 

 fresh- water species. There is a great deal of variation within a species 

 with respect to cell shape and manner of branching, apparently 

 related to environmental conditions. The interpretations of these 

 variations by taxonomists, and the limitations which have been set 

 up to define species in the genus are conflicting. A great deal of 

 confusion has arisen in the literature because these variables and 

 intergrading forms have been separately described. An examination 

 of supposedly authentically named herbarium material is of little 

 help to the student, because the specimens frequently are not in 

 agreement with the original descriptions. There is a great need, 

 therefore, for a monographic review of the genus and a clarification 

 of the synonymy which exists among the names attached to her- 

 barium specimens and in the literature. 



Most of the species found in our region are free-floating, lacustrine 

 forms. Several of these show considerable variation according to 

 whether they are in quiet backwaters or are subjected to wave 

 action. Those which seem to have clear-cut characters are listed, 

 together with some of their varieties, and an attempt has been made 

 to describe those expressions which are most likely to be found in 

 this area. Many collections have been set aside for further study. 

 Although the following key is of limited value, it may serve to se- 

 parate the species which I consider recognizable in our collections. 



Key to the Species 



1. Plants growing at great depths (10-50 meters); permanently 

 attached; branching very irregular and interlacing, the branches 

 arising from below the apex of the cell C. profunda var. Nordstedtiana 



1. Plants not growing at great depths; branches less irregular, arising 



from the apices of the cells of the niain axis — 2 



2. Plants permanently attached, mostly in flowing water, forming 



feathery tufts of repeatedly branched filaments — 3 



2. Plants free-floating, at least when mature; when attached, 



coarser and less regularly branched than above 4 



3. Branching increasing toward the upper portions of the 



frond to form dense terminal tuf ts - C. glomerata 



3. Branching decreasing toward the upper portions of the 



frond to form penicillate tufts C callicoma 



4. Filaments very crooked and bent; cells ovate or pyriform, 



or irregularly swollen - — -C. fracta 



( See also the varieties of C. fracta, some of which have cylin- 

 drical cells, although the filament is still rather crooked and does 

 not show the definite arbuscular habit of the species mentioned 

 below. ) 

 4. Filaments straight; cells cylindrical or very slightly swollen — 5 



r 136 1 



