122 ' Rhodora [JuLy 
THE GENUS PILINIA. 
Е. 5. COLLINS. 
Plate 77. 
In a previous paper! the writer noted the occurrence of Pilinia 
rimosa Kütz. in Maine, and made some comparison of the species 
with the plant known as Acroblaste Reinschii Wille. There is noth- 
ing to add in regard to the former species, but observations made on 
forms of Acroblaste from various stations indicate that all can best be 
included under Pilinia, with somewhat changed definition, as fol- 
lows:— 
Basal layer of abundantly branched filaments, from which arise 
erect filaments, simple or branched, sometimes terminating in articu- 
late hairs; chromatophore covering the cell wall; sporangia roundish, 
ovoid or clavate, terminal or lateral on erect filaments, or sessile 
on the basal layer, the contents forming numerous biciliate zoo- 
spores, which escape through an opening at the summit, development 
unknown. 
With this extension the genus will include six American species, 
all marine, P. rimosa and P. maritima occurring also in Europe, the 
others known only in America; P. maritima connecting it with Chae- 
tophora and originally placed in that genus by Kjellman; P. Lunatiae 
and P. minor at the other end coming close to Gongrosira. "Тһе fol- 
lowing key may be found convenient in distinguishing the species. 
KEY то THE AMERICAN SPECIES OF PILINIA. 
1. Filaments often ending in hairs. Р. maritima. 
1. Hairs not present. 2. 
2. Erect filaments short, densely packed. 3. 
2. Erect filaments longer, yellowish. 4. 
3. Dark green; filaments 8-12 м diam.; on live shells. P. Lunatiae. 
3. Yellowish green; filaments only 2-5 # diam.; on pebbles. P. minor. 
4. Forming a rather firm, spongy coating on woodwork. P. rimosa. 
4. Forming a thin, soft coating. . 
5. On shells, pebbles, ete.; sporangia on erect filaments. Р. Reinschii. 
5. On woodwork; sporangia on basal layer, rarely lateral on erect fila- 
ments. P. Morsei. 
1 Collins, Notes оп New England Algae, Ruopora, Vol. V, p. 207, 1903. 
