1^8 Minnesota Algae 



Plate VI. fig. 14, IS- 



Plant mass cushion-shaped, stony, hardened with calcium carbonate, 

 becoming confluent into a crustaceous, mammillate layer, blue^green, flesh- 

 colored or brownish on the surface, zonate within; filaments slender, flex- 

 uous, closely entangled, forming a trunk-shaped basal portion narrower 

 at the base, thicker above, branched and divided into many parts at the 

 apex; false branches fasciculate, somewhat appressed; sheaths somewhat 

 thick, with pointed apex; trichomes 1.4-3 inic- in diameter, constricted at 

 the joints, many in the trunk-shaped basal portion, few or solitary in the 

 branches; apical cell acute conical; cells 1.2-3.5 mic. in length; cell con- 

 tents pale blue-green. 



Connecticut. Mixed with other algae. Twin Lakes, near Salisbury. 

 (Setchell). Michigan. Pebbles found in a pond on the shore of Lake 

 Michigan. (Velie). Minnesota. Forming calcareous pebbles, which were 

 found lying in from four to ten feet of clear water on sand-bars. Clear- 

 water Lake, Wright County. June 1901. (Freeman and Lyon). "These 

 pebbles range in size from that of a small hickory nut to two inches in 

 diameter. Most of them are flattened, and though comparatively smooth 

 in same cases, are often rough, corrugated and wave-worn. All are more 

 or less hollow. In section they have a distinctly stratified appearance." 

 * * * They "were found to be composed of a densely interwoven mass 

 of filaments of which the most common type was that of S. fasciculata 

 Com." — Powell. 



285. Inactis lacustris (A. Braun) De Toni. Syll. Algar. 5: 354. 1907. 



Gomont. Monogr. Oscill. 39. pi. 6. f. 9-12. 1893. (Schizothrix 



lacustris A. Br.). 



Collins, Holden and Setchell. Phyc. Bor.-Am. Fasc. 15. no. 712. 1900. 



Saunders. The Algae. Harriman Alaska Expedition. Proc. Wash. Acad. Sci. 



3: 397. 1901. 



Plate VI. fig. 16. 



Plant mass cushion-shaped or crustaceous, not at all or scarcely hard- 

 ened with calcium carbonate, dull yellowish green; filaments flexuous, 

 closely crowded, forming a trunk-shaped basal portion narrower at the 

 base, broadened towards the apex, branched and divided into many parts 

 at the apex; false branches twisted, entangled, or somewhat parallel; 

 sheaths colorless, wide, very wide in the lower part of the filament; trich- 

 omes i-i.S mic. in diameter, constricted at the joints, many in the trunk- 

 shaped basal portion, remote, often spirally twisted, few or solitary in the 

 branches; cells up to 4 mic. in length; cell contents pale blue-green. 



Alaska. In a fresh water pool. Near Prince William Sound. June 1899. 

 (Saunders). Connecticut. On sandy ground near "Fresh Pond" (brack- 

 ish). Stratford. December 1897. (Holden). 



Var. caespitosa Gomont. 1. c. 39. De Toni. 1. c. 354. 



Hauck and Richter. Phyk. Univ. no. 741. 1886-1889. (S. lacustris 

 caespitosa Gom.). Collins. Algae. Flora of the Blue Hills, Middle- 

 sex Fells, Stony Brook and Beaver Brook Reservations of the Metropoli- 



