SPECIES OF ALG^. 53 



49. PROTOCOCCUS. 



§ Aerial forms (a). 



§ Aquatic (c). 



a. Cells without gelatinous envelope (i). 



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



pressure angulosa, i8i 



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



viridis, 181 

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



dissectus, 18 r 



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, -l?i2; gigas, 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 35-70/1 . . . gigas, 184 



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



a. " 3 angled, diameter i2-i5yu . .... 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, 185 

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



51. DICTYOSPHjERIUM. 



a. Cells ovate or subglobose . . Ehrenbergianum, 186 



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



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



52. HYDRURUS. 



One very variable species .... . fmtidus, 187 



53. PALMODACTYLON. 



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



more rows ... . variwn, 189 



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



