196 



found on this examination consisted of Chrootheca RicJiteriana 

 Hansg., Gleocapsa aeruginosa (Carmichael) Kuetzing, G. gelatinosa 

 Kuetzing, G. quarternata (Brebisson) Kuetzing and Gleotheca 

 linearis Naegeli. Attached to a small red alga (not identifiable) 

 which was fastened to a piece of stalactite was found Microcystis 

 fios-aqua (Wittrock) Kirchner. The most abundant blue-green 

 alga was Chrootheca Richteriana Hansg., which, according to 

 Josephine Tilden, consists of a somewhat gelatinous plant mass, 

 thick, or more or less expanded of a blue-green, or yellowish color. 

 The cells found in these masses are 18-24 microns in diameter, 

 once to twice as long as wide, single, or in pairs, with thick sheaths 

 up to 6 microns in diameter. This species, figured by Miss 

 Tilden, has been reported from Bermuda by Farlow and from 

 Montego Bay, Jamaica, by Pease and Butler. Of the three 

 species of Gleocapsa enumerated above, the following is the 

 distribution recorded in the Minnesota Algae: 



G. aeruginosa Greenland, New York, West Indies (Porto Rico). 



G. gelatinosa United States, West Indies. 



G. quarternata West Indies, Hawaii. 

 The note with reference to G. aeraginosa in Minnesota Algae is 

 apropos: "West Indies. Forming a dark green layer on stone 

 in cave. 'El Convento,' near Penuelas, Porto Rico (Sintenis) '^ 

 Gleocapsa quarter?iata is described as forming a gray-green, muci- 

 laginous coating on wet cliffs in Hawaii. The distribution of 

 Gleotheca linearis is given in Minnesota Algae, as: "West Indies, 

 On damp walls of dam. Sharp's River, St. Vincent (Elliott)." 



That these algae are active in the formation of the stalactites 

 is indicated by their close attachment to the surface of the sta- 

 lactites in the Devil's Hole, Bermuda. They remove in the 

 case of the carbonated waters, containing calcium bicarbonate 

 (CaHC03)2 in solution, the gaseous carbon dioxide, which is 

 used by the blue-green algae in photosynthesis of organic com- 

 pounds, so that the stalactites are formed by the continual 

 deposit of calcium carbonate (CaCOs). Josephine Tilden has 

 studied the formation of algal stalactites in the Yellowstone 

 National Park, where such algae as Gleocapsa violacea, Phormidium 

 (Leptothrix) laminosum, Schizothrix calcicola and Synecococcus 



