30 



Dansk Botanisk Arkiv, Bd. 3. Nr. 1. 



often two opposite branchlets (Fig. 21). In the lowest part of 

 the plant these branchlets consist of 2—3, rarely more cells, 

 higher up of two, then of a single one only ; at the top some 

 few sessile sporangia may occur. The cells in the branchlets 

 are about S/x broad and S/j. long. 



The sporangia are ovate about 7 — Sju broad and 8 — 10 ft long. 



This species has been found at the very exposed coast at Northside, 

 St. Croix. 



7. Acrochætium Sancti Thomæ nov. spec. 



Thallus sine pilis usque ad 200 — 300 /^ altus. Discus basalis 



unistratus, e fdis re- 

 pentibus plus minus 

 lateraliter confluenti- 

 bus, compositus. 



Fila erecta sim- 

 plicia aut parce ra- 

 mosa, e cellulis 8 — 

 9// latis et 16 — 18// 

 longis composita. 



Chromatophorum 

 parietale, pyrenoide, 

 ut videtur, centrali 

 instructum. 



Pili longi hyalini, 

 initio terminales, po- 

 stea pseudolaterales, 

 adsunt. 



Monosporangia 

 plerumque sessilia et 

 uniseriata, interdum 

 pedicellata et oppo- 

 sita, solitaria vel bina 

 in uno articulo, ob- 

 ovata, 7 // lata et 

 10 fj. longa. 



This plant was 



found together with 



T.. oo ^ , • c^ ■ rr.j several other species 



Fig. 2ö. Acrochætium Sancti I homæ nov. spec. i i i e 



a, b, c, three parts of different tufts showing upon old leaves ot 



sporangia-bearing filaments, d, e, bases of Sargassum vulgare 



plants, f, basal filaments seen from above. p • n . p. 



(a, about250:l,fc,c,e, 130:1, /•, 250:1, rf, 500:1). formmg small tutts. 



