CALOTHRIX. 237 



CALOTHRIX DILLWYNII, Hass. 



Flaccid, aeruginous (blue-green) or more rarely brownish ; 

 sheaths inconspicuous, except sometimes towards the base ; 

 articulations, 1-11 times as long as the diameter; heter- 

 ocysts at the base of the spurious branches, ovate or 

 sometimes cordate. Diameter of trichomes, 12-15 yu ; smaller 

 forms, 10-13 jn. The latter sometimes with twin heterocysts. 



The larger from specimen from Garrett County, Maryland. 

 The other from swamps, etc., New Jersey. 



Plate CLXVIII, figs. 3, 4. 



CALOTHRIX GYPSOPHILA, Kg. 



Brown, or almost black, smooth, shining, in small tufts, 

 or extended strata on rocks at water's edge washed by the 

 waves. Trichomes about one-fourth of an inch long, sub- 

 dichotomously branched, somewhat attenuated at ends ; 

 sheath rather close, brownish yellow. Articulations indis- 

 tinctly a-1 diameter. Heterocysts the size of trichome, 

 usually two or three in series. 



Diameter of filaments, 12-14 yw. 

 Syn. Scliizosiplion gypsopliilus, Kg. 



Lake Hopatcong, New Jersey. 



Plate CLXVIII, fig. 5, two short filaments with spurious 

 branches. 



Have adopted this name although our plant is not in every 

 particular in accord with the diagnosis given in Raben- 

 horst's Flora Algarum. 



Plate CLXVIII, figs. 6, 7. 



Smaller variety from Pennsylvania, and from Minnesota. 



CALOTHRIX GRACILIS, Bab. 



Small tufts, aeruginous, or later dull brown, usually fasci- 

 culately branched ; branches closely attached ; sheath firm, 

 close, colorless or light yellow, indistinctly lamellate, ends 

 closed, attenuate, except in older, brown plants, then often 

 open and fibrous. Heterocysts oval, yellow, same size as the 

 filaments, single or twin. 



Diameter of basal parts of trichomes, 6-8 /*. 



Syn. ScMzosiphon gracilis, Eab. 



Occurs frequently in ponds; differs from C. Dillwynii 

 mainly in size. 



Plate CLXXIII, figs. 2, 3. 



