1920] 8etchell-Gardncr : Chlorophyc&ae 231 



Spongomorpha coalita, as it usually occurs, is readily recognizable, 

 both by its habit and by the possession of compound, strongly hooked 

 branchlets. It seems reasonably certain that the Conferva scopae- 

 formis Ruprecht represents only a younger stage of C. coalita 

 Ruprecht, with somewhat more slender filaments and longer terminal 

 segments (cf. Collins, 1909, p. 361). The plants are distinctly 

 elongated and their filaments are combined into ropelike masses. The 

 recurved branchlets usually show either three or four sharply recurved 

 and pointed tips or a less number, sometimes only one, with one or 

 more longer straight branchlets arising from them. We have seen 

 nothing like this in any other of our species of Spongomorpha, nor is 

 any branching of this sort described for any of the species of this 

 genus, or of Acrosiphonia, except that Kjellman figures compound 

 recurved branchlets in his Acrosiphonia hamulosa (1893, pi. 1, f. 5). 

 This species, however, is of very different habit, and has more slender 

 filaments as well as more slender recurved branchlets than Spongo- 

 morpha coalita, resembling more closely S. spinescens, but seemingly 

 distinct from it. 



There is considerable variation in the dimensions of the filaments 

 and in the proportions of the segments in different individuals. The 

 walls of the segments also vary much in thickness, up to as great 

 as 40/x, e.g., in a specimen collected on the west coast of Whidbey 

 Island, Washington (Gardner, no. 467). 



A seemingly young, but unusual plant, collected on June 3 at 

 Carmel Bay, California (no. 5418 Setchell), is about 200ix in diameter 

 at the tips, but the terminal segment is often as much as 3 mm. long. 

 Below, the hooked branchlets are often simple, but some are com- 

 pound. If separated, these specimens might be referred under Con- 

 ferva scopaeformis Rupr. 



15. Microdictyon Dec'ne 



Plant a sessile, membranaceous network, formed of monosiphonous 

 filaments, densely branching in one plane in a radiate manner, the 

 tips of the branches attaching themselves to the sides of other branches 

 by a terminal thickening, producing irregular, angular, open spaces 

 between the segments; reproduction by zoospores formed in any 



segment. 



Decaisne, PI. de I'Arab., 1841, p. 115. 



