SPECIES OF ALGJE. 53 



49. PROTOCOCCUS. 



Aerial forms (a). 



Aquatic (c). 



a. Cells without gelatinous envelope (fr). 



a. Cells with gelatinous envelope in which they divide; angular from 



pressure angulosa, 181 



b. Common everywhere on trees, fences, etc.; cells yellowish green, 



viridis, 1 8 1 

 b. On moist old wood; cells dark green; decussately dividing, 



dissectus, 181 



b. On pots, etc., in green-houses; orange, reddish-brown, yellowish 



green miniatus, 182 



c. Beset with small spines or hairs vestitus, 183 



c. Smooth, in gelatinous tegument, . . . humicola, 1^2 \ gig as, 183 



c. " not in tegument (d). 



d. Cells clustered somewhat grape-like botryoides, 182 



d. Cells single, membrane thick, often lamellate . . Wimmeri, 183 

 d. Cells varying in size, membrane not lamellate . . infusionum, 182 



50. POLYEDRIUM. 



Angles rounded, not spinous (a) 



" bifid or trifid (b). 



" spinous or greatly elongated (c). 



a. Cells 4 or 5 angled, diameter 35-70^ gigas, 184 



a. " 4 angled, diameter 8-io/f minimum, 185 



a. " 3 angled, diameter 12-1 5^ muticum, 185 



b. Angles bifurcate, sharply tipped bifurcatum, 184 



b. " often repeatedly bilobed, hyaline, acute . . enorme, 184 



c. Centre scarcely body-like, radii thin, much prolonged, 



longispinum, 1 85 

 c. Centre distinctly a body; angles spinous . tetragonum, minus, 184 



51. DICTYOSPH^ERIUM. 



a. Cells ovate or subglobose Ehrenbergianum, 186 



a. Cells reniform, about twice as long as wide . . reniforme, 186 

 a. Cells oval, often centrally constricted .... Hitckcockii, 186 



52. HYDRURUS. 



One very variable species fcetidus, 187 



53. PALMODACTYLON. 



a. Family of cylindrical, bladder-like radiating cases; cells in i or 



more rows varium, 189 



a. Family simple, not branched, more filamentous . . simplex, 189 



