1920] Setchell-Gardncr: Chlorophyceae 233 



Order 4. UL VALES blackman and tansley 



Fronds membranaceous of one or two layers of cells, or tubular 

 with wall of a single layer of cells, or filamentous of two or more 

 vertical rows of cells, simple or branched, attached by rhizoids either 

 free or united into a disk; cells with a single nucleus and a single 

 parietal chromatophore containing usually one, but, occasionally, two 

 or three pyrenoids; multiplication vegetative, non-sexual and sexual; 

 vegetative, by abscission of proliferous shoots, by accidental rupture, 

 by gemmae or by akinetes; non-sexual, by 2- or 4-ciliated zoospores; 

 sexual by 2-ciliated isoplanogametes forming a zj'gote capable of 

 germinating at once. 



Blackman and Tansley, Rev. Class. Green Algae, 1902, pp. 20 and 

 136; West, Algae, 3916, vol. 1, p. 275. 



FAMILY 9. ULVACEAE greville 



Characters of the order. 



Greville, Alg. Brit., 1830, p. 168 (lim. mut.). Ulvacees Lamouroux, 

 Essai, 1813, p. 59 (in part) ; Thuret, Note sur la Syn., 1854, p. 27. 



Key to the Genera 



1. Frond tubular even at maturity 2 



1. Frond expanded at maturitj' 4 



2. Frond parenchymatous (except E. groenlandica) 



19. Enteromorpha (p. 244) 



2. Frond not parenchymatous 3 



3. Cells gloeocai)soid in longitudinal strij)s 17. Capsosiphon (p. 238) 



3. Cells neither gloeocapsoid nor in longitudinal strips 



Enteromorpha groenlandica (p. 248) 



4. Frond narrow, 1-4 cells wide 21. Percursaria (p. 273) 



4. Frond broad, meml)ranaceous 5 



5. Mature frond of a single layer of colls 18. Monostroma (p. 235) 



5. Mature frond of two layers of cells, united wholly or in part 2U. Ulva (p. 260) 



17. Capsosiphon Gobi 



Plants filamentous, hollow, gelatinous, tlie cells mostly in twos and 

 fours, enclosed witliiii the Avails of the mother cell, and arranged in 

 distinct longitudinal series, the series loosely connected laterally. 



Gobi, Ber. Alg. Forsch. im Finn. Meer., 1877, etc., 1879, p. 88. 

 Ilea Fries, Syst. orb. veg., pt. 1, pi. homon, 1825, p. 336 (in part) ; 

 J. G. Agardh, Till Alg. Sys., pt. 3, 1883, p. 114. 



