144 COLLINS AND HERVEY. 



Var. PATENTISSIMUM (Harv.) Farlow, 1881, p. 138; C. arachnoideum 

 var. patentissimum Harvey, 1853, p. 217, PI. XXXIII. B. Heron 

 Bay, Jan., Hervey. The frequent wide forkings give a habit quite 

 different from the typical form, but there is agreement in essentials. 



Var. ARACHNOIDEUM (Ag.) J. G. Agardh, 1851, p. 117; 1876, p. 94; 

 P. B.-A., No. 2098. C. arachnoideum Harvey, 1853, p. 217; C. dia- 

 phanum var. arachnoideum Agardh, 1824, p. 134. On Cymodocea 

 and various algae, Grasmere, Feb., Harvey. A very slender and 

 delicate form, but otherwise like the typical form. 



Var. PYGMAEUM (Kiitz.) Hauck, 1888, p. 460; P. B.-A., No. 2193; 

 Hormoceras pygmaeum Kiitzing, 1862, p. 23, PI. LXXV. On Codium 

 decorticatum, Cooper's Island, Aug., Collins. With tetraspores. 



2. C. cruciatum sp. nov.; P. B.-A., No. 2192. Minuta, ad 

 algas alias repens; filamentis prostratis circa 200 /JL diarn., cylindricis 

 vel ad nodos leviter constrictis, rhizoidis unicellularibus incoloratis 

 affixis; filamentis erectis passim ad nodos evolutis; apice filamenti 

 prostrati assurgente, in filamentum erectum transformato; cellulis 

 inferne circa 3 diam. longis, superne brevioribus, prope apicem diarn- 

 etro brevioribus; ramulis penultimis 80-100 fj. diam.; ramis repetite 

 dichotomis, cellulis cylindricis vel plus minusve ad nodos constrictis; 

 apicibus forcipatis; corticatione cellulis sensu filamenti elongatis 

 constante, irregulariter positis, zonam arctam formante margine 

 inaequali. Protoplasma cellularum inferiorum subcylindricum, 

 superiorum subsphaericum, fasciis tenuissimis longitudinalibus notata, 

 raro anastomosantibus, nee longitudinem cellulae aequantibus, 

 plerumque spatio latitudinem fasciae aequali separatis. Tetra- 

 sporangiis ovoideis, circa 50 X 35 /JL, membrana 6 /j. crassa non in- 

 clusa, 1-4 ad nodum, cruciatis, modo regulariter, modo decussate; 

 aut singulis ad nodum, seriem externalem longitudinalem forrnantibus, 

 aut pluribus nodum circumdantibus; dimidio sporangii extra corticem 

 emergente. Plate IV, figs. 27-28. 



Minute, creeping on other algae; prostrate filaments of about 

 200 n diam., cylindrical or slightly constricted at nodes, attached by 

 unicellular, colorless rhizoids, issuing from the nodes; erect filaments 

 occasionally arising at nodes; apex of prostrate filament becoming 

 erect and assuming the character of an erect filament; cells about 

 3 diam. long below, diminishing towards the apex, to less than one 

 diam.; penultimate branches 80-100 /* diam.; branches repeatedly 

 forking, cells cylindrical or with nodes more or less constricted; 

 apices forcipate; cortication consisting of cells elongate in the direc- 

 tion of the filament, in no definite order, band narrow, edge uneven. 



