THE GREEN ALGAE OF NORTH AMERICA 291 



up to 50 fji diam., developing into an orange colored akinete, or 

 else developing into a sporangium producing 16 or more biciliate 

 zoospores. On submerged wood, stones, and shells ; fresh water. 

 Fig. 91. Cal. Europe. 



20. CHLOROTYLIUM Kiitzing, 1843, p. 285. 

 Frond consisting of erect, branching, articulate filaments, 

 forming bright green, firm, pulvinate coatings, sometimes in- 

 crusted with lime ; cells with band-shaped chromatophore, 

 (with pyrenoid ?) ; asexual reproduction by biciliate zoospores, 

 formed in large numbers in the cells ; also by 4-ciliate zoospores 

 formed 4-16 each in small cells, resulting from division of the 

 vegetative cells ; also by akinetes. Fresh water. 



C. CATARACTARUM Kiitzing, 1843, P- 28 5> PI- XVII; Phyc. 

 Univ., No. 290. At first in minute tufts, up to 4 mm. diam., 

 soon confluent to a continuous layer; filaments parallel, densely 

 packed, 6-12 yu. diam., of two kinds, one kind bright green, cells 

 i^j-2 diam. long, the other lighter, nearly hyaline, cells 2-6 

 diam. long ; akinetes orange or vermilion, formed only from the 

 shorter cells, 9-15 /* diam., globose or oblong-ellipsoid. Fig. 86. 

 N. Y., Ky. Europe. 



21. PILINIA Kiitzing, 1843, p. 273. 



Basal layer of abundantly branched filaments, from which 

 arise erect filaments, simple or branched, sometimes terminating 

 in articulate hairs ; chromatophore covering the cell wall ; 

 sporangia roundish, ovoid or clavate, terminal or lateral on 

 erect filaments or sessile on the basal layer, the contents form- 

 ing numerous biciliate zoospores, which escape through an 

 opening at the summit ; development unknown. 



KEY TO THE SPECIES OF PILINIA. 



i. Filaments often ending in hairs. 7. P. uiaritiiua. 



i. Hairs not present. 2. 



2. Endopbytic. 3. P. endophytica. 



2. Not endophytic. 3. 



3. Erect filaments short, densely packed. 4. 



3. Erect filaments longer, yellowish. 5. 



4. Dark green ; filaments 8-12 n diam.; on live shells. 



i. P. Ilunatiae. 

 4. Yellowish green ; filaments 2-5 n diam.; on pebbles. 



2. P. minor'. 

 5. Forming a rather firm, spongy coating on woodwork. 



5. P. i-iinosa. 



5. Forming a thin, soft coating. 6. 



