SPECIES OF ALG^E. 51 



b. Outer circle 14, inner 7, centre closed by i; outer spaces 7, inner 4, 



simplex var., 153 



b. Outer circle 12, inner 4, centre open; outer spaces 4, 



duodenarius, 153 



b. Outer circle 14, inner 7, centre closed by 4; outer spaces 7, inner 4, 



simplex var., 153 



<r. Marginal cells 2-lobed, each cuspidate; cells 8-16-128; centre closed, 



Boryanum, 153 



d. Perforated by small openings brachylobum, 154 



d. No openings; centre closed; .... muticum, angulosum, 153 



e. Perforate by small openings, or centre open (/). 



e. Not perforate, centre closed (g). 



f. Cells 16-32-64 pertusum, 154 



f. Cells 6, centre open angulosum, var., 154 



. Apices converging, space between oval . . . forcipatum, 153 



g. Apices not converging (ti). 



h. Each apex 2-lobed, sometimes diverging . . Ehrenbergii, 154 



41. HYDRODICTYON. 



One species utriculatum, 169 



42. COELASTRUM. 



a. Cells globose, with interstitial openings . . . microporum, 170 

 a. Cells angular, each with a tubercular process . cambricum, 170 



43. SORASTRUM. 



One species spinulosum, 171 



44. STAUROGENIA. 



One species . crudatum, 171 



45. SCENEDESMUS. 



Cells armed with spines (d). 

 Cells not armed with spines (e). 

 a. Aquatic (b). 



a. On moist sand, Florida; cells 2-4, fusiform, 



antennatus, var. rectus, 172 



b. Cells oblong, cylindrical, ovate or globose (c). 



b. Cells, some at least, spindle-shaped (d). 



c. Spines recurved on outer cells caudatus, 172 



c. Spines straight, single or sometimes two . . . polymorphus, 173 



c. Spines straight, three to five rotundatus, 174 



d. Inner cells fusiform, armed, outer lunate, . . . dimorphus, 173 

 d. Fusiform, oval or globose; spines straight . . polymorphus, 173 



