Key to the Species 



1. An elongate, cartilaginous, branching thallus, sometimes short and 



arbuscular when young or when growing in warm water C. incrassata 



1. A globose or hemispherical, tuberculose thallus, 1-10 mm. in diameter — 2 



2. Colonial mucilage rather soft; filaments irregularly branched, 



spreading and entangled C. elegans 



2. Colonial mucilage firm; filaments erect and evidently radiating from 



a common center within the colonial mucilage 3 



3. Branches fasciculate toward the outer limits of the thallus; 



cells 3-6 times the diameter in length C. pisiformis 



3. Filaments radiating and subparallel; branches not fasciculate near 

 the outer limits of the thallus; cells up to 10 times 

 their diameter in length C. attenuata 



Chaetophora attenuata Hazen 1902, p, 213 

 PI. 13, Figs. 4, 5 



Forming attached, firm, gelatinous globules, 2-5 mm. in diameter, 

 having radiating, nearly parallel, erect branches from numerous 

 basal, rhizoidal processes. Filaments usually dichotomously (some- 

 times trichotomously ) branched, ending in sharply pointed, setif- 

 erous cells; branches not fasciculate, but loose and evenly developed 

 from the main axis and much elongated. Cells 5-6/a in diameter, 

 15-30/. long. 



This is a fairly common species, often found in cold water, form- 

 ing green globules on old leaves and submerged wood, gregarious 

 but distinct from one another. Mich., Wis. 



Chaetophora elegans ( Roth ) C. A. Agardh 1812, p. 42 



PL 14, Figs. 3, 4 



Thallus attached, globose or flattened green masses of soft muci- 

 lage; colonies often confluent with one another to form irregularly- 

 shaped masses, in which dichotomous filaments spread out from a 

 common center. Branches rather loose; branches of the second order 

 somewhat more numerous near the upper part of the thallus, ending 

 in abruptly pointed ( rarely setiferous ) cells. Cells 7-12/i, in diameter 

 in the main axis, 15-30/1, long. 



This is the most common species of the genus in our collections, 

 appearing in many lakes and streams. Overhanging grass in shallow 

 water may be a solid green gelatinous mass formed by numerous 

 confluent colonies of the species. Mich., Wis. 



Chaetophora incrassata (Huds.) Hazen 1902, p. 214 

 PI. 14, Figs. 1, 2, 11 

 Thallus attached at first, free-floating when mature, forming tufted 

 or arbuscular lobed and cartilaginous masses, varying from a few 



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