192 ' : ■ Rhodora [October 



sparingly branched, branches erect, secund, sometimes sUghtly 

 tapering, hairs not observed; spores 9 X 16 ;i, sessile on the upper 

 side of the branches, solitary or sometimes in secund series, one on 

 each cell of the branch; at the base of each primary filament a rounded 

 cell, the original spore, emitting a short, descending ])rocess, some- 

 times branched, of a few small rounded cells, attached to the host. 

 On Dasya elegans (Mart.) Ag., Wood's Hole, Mass., Sept. 2, 1905. 



This is the only species of Acrochaetium in which the spore is ])er- 

 sistent; the color being the same as that of the host, there is nothing 

 to show the presence of the Acrochaetium without microscopic exami- 

 nation. No authentic specimen has been seen of Harvey's plant on 

 Dasya, but there is every reason to suppose that if Harvey had seen 

 this species, he would have included it in his Callithamnion virga- 

 tuhmi; it is, however, distinct from the C. rirgatuhim of Wyalt, 

 Algae Danmonienses, No. 1<S9, which must be considered as authentic. 



A. Alariae (Jonsson) Bornet, 1. c, p. XIX; Chantransia Alariae 

 J6nsson, Botanisk Tidsskrift, Vol. XXIV, p. 132, fig. 1 ; C. Kccnndaia 

 Phyc. Bor.-Am., No. 23G. Filament arising from a single cell, naked 

 below, usually densely branched above, branches opposite, alternate 

 or secund; sterile filaments often bearing hairs; filaments about 10 /< 

 diam. below, 8 /< above, cells 1-3 diam. long below, up to (5 diam. 

 long in sterile branches. In fertile branches uniformly short often 

 clavate, each cell bearing two opposite, sessile spores about 14 X 20 ,«, 

 a similar spore terminal on the branch. On Alaria csculcnia, Maine 

 and N. H. 



A. Saguaeaxum (^Nlont ) Bornet, 1. c, p. XXI; Cladophora Sagrac- 

 ana Montague, Sylloge Algarum, p. 459; Chaniransia virgatitlaF. B.- 

 A., No. 39. Basal layer of contorted and entangled filaments, from 

 which arise erect filaments, G-10 fi diam., cells 4-8 diam. long, branch- 

 ing not very dense, the lowest branches longest, upper gradually 

 shorter, all rather erect, bearing short secund raniuli above the axils; 

 spores borne on the ramuli, about 10 X 15 /(, one or two on each artic- 

 ulation. Conn., W. I., Florida, Southern California. 



The ramification is like that of A. Daviesii, but the basal layer is 

 quite different. 



A. FLEXUOSUM Vickers, Ann. Sci. Nat., Series 9, Bot., Vol. I, p. 60. 

 Forming dense globular tufts, with basal entangled horizontal fila- 

 ments, from which arise erect fiexuous filaments, 10 /( diam., branch- 

 ing above, branches gradually shorter upwards, in secund series. 



