CALOTHRIX. 239 



CALOTHRIX HOSFORDII, Wolle. 



Stratum olivaceous, trichomes aggregated, bright aerugi- 

 nous, subdichotomously spuriously branched ; branches 

 flagelliform, turgid below, tapering to a fine, colorless hair- 

 point. Articulations 4-5 to diameter. Sheath wide, dis- 

 tinctly lamellose, yellow toward the base ; colorless and 

 hyaline toward the ends. Heterocysts depressed semi-glo- 

 bose ; 3-4 times broader than long ; bluish tint, somewhat 

 lighter than the vegetative cells. 



Diameter of internal trichome, thicker parts, 10-12 ju. 

 Diameter of sheath, 25-28 yw. 



Collected by F. H. Hosford, in pond near Charlotte, Ver- 

 mont. Bears some resemblance to the last, C. Brebissonii, 

 but is particularly distinct in the form and color of the 

 heterocysts. 



Plate CLXIX, figs. 1, 2, a long filament with numerous, 

 young forms, spurious branchlets, attached ; figs. 3, 4, three 

 young, isolated plants. 



CALOTHRIX LACUCOLA, Wolle. 



Floating, dull yellow or brownish, dichotomously 

 branched ; branches somewhat patent, not concrete, mod- 

 erately attenuated, apices obtuse, slightly bent. Internal 

 trichomes thin, dull aeruginous or yellowish brown, homo- 

 geneous or indistinctly articulate, subequal or less. Hetero- 

 cysts globose, yellow, single or twin, at base of branchlets. 



Diameter of thicker parts, 15-20 //. 



Split-rock Pond, New Jersey, the only habitat hitherto 

 found. 



This singular plant bears a resemblance to Tolypothrix, 

 but is unlike the forms of that genus in having the filaments 

 attenuated, beside the distinct branching. 



Plate CLXXII, fig. 1, one of the larger forms. 



CALOTHRIX CRUST ACEUM, ( Ag. ) Wolle. 



Plants densely caespitose, erect, somewhat regularly 

 branched, branches free, with obtuse rounded apices, and 

 each with a heterocyst at the base. Aeruginous endochrome 

 annulated, increasing in diameter towards the apices of the 

 filaments. 



Diameter sheath, 17-20 yw. 



Diameter of internal filaments, 8-10 yw more or less. 



This plant has been variously described in its different 



stages of development. 



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