1906] Collins, — Acrochaetium and Chantransia 193 



erecto-patent, cells 2-3 diam. long; spores secund on the ramuli. 

 On Chactomorpha, N. J., Barbados. 



In dimensions, and in arrangement of spores like A. seciindatum; 

 basal layer different. 



A. Dictyotae n. sp. Fills primariis 12-14 n crassis; ramulis 10- 

 12 ,u; longitudine cellularum inferne 1^ diam. aequante, ad 4 diam- 

 superne; ramulis pleruraque secundatis, parum attenuatis, plerumque 

 obtusis; monosporis 14 X 20 /(, in fills sessilibus in loco ramuli, vel 

 1-3 terminalibus in ramo uni- vel bicellulari; cellulis ad basin 

 frondis rotundatis vel subquadratis, interdum in discum coalitis 

 plures frondes sustinentem; disco fila irregularia emittente, stratum 

 corticalem plant ae hospitis penetrantia, inter cellulas magnas inter- 

 nas repentia, interdum usque ad superficiem oppositam attingentia. — 

 Main filaments 12-14 ju diam.; ramuli 10-12 fi; cells from 1^ diam. 

 below to 4 diam. above; branches mostly secund, not much tapering, 

 usually with rounded tips; spores 20 x 14 ,«, sessile on the filament in 

 the place of a branch, or one to three at the end of a one- or two-celled 

 branch. At the base the cells are rounded or squarish, sometimes 

 forming a disk from which arise several fronds; and from which 

 irregular filaments issue, penetrating the cortical layer of the host, 

 and passing between the large internal cells, sometimes extending 

 through to the surface on the other side. On Dicii/ota Binghamiana 

 J. Ag., in tide pools near high water mark, La Jolla, California, Aug. 

 21, 1899. Mrs. E. Snyder. 



No other of our species has so extensive an endophytic portion. 



A. viRGATULUM (Harv.) Bornet, 1. c, p. XXII; Callithamnion 

 virgatulum Harvey in Hooker, British Flora, Vol. II, p. 549; Tren- 

 tepohlia virgatula Farlow N. E. ^Marine Algae, p. 109. One to many 

 filaments arising from a basal disk; filaments 10-14 p. diam. below, 

 long and straight, with rather few long straight erect branches, 6-8 /< 

 diam. near the end, usually terminating in a very slender hair; cells 

 about 3 diam. long below, about 6 diam. in the branches; short 

 ramuU, mostly 1-3-celled, abundant, scattered, opposite or in short 

 secund series, bearing either hairs or terminal spores; spores also 

 sessile on the branches, occupying the places of ramuli, 12 X 20 ju. 

 On various algae, ISIaine to N. J. 



The long subsimple branches, with short ramuli or spores on 

 nearly every cell, and the abundant hairs, are the chief characteristics 

 of the species. The branches do not gradually taper into the hairs; 



