F. Børgesen: Rhodophyceæ of the Danish W. Indies. 



51 



The germinating spore grows downwards through the thick 

 peripheral wall of the host plant until it arrives at the more 

 compact innerwall of the cells. Here it ramifies 

 sending out some few short horizontal branches 

 (Fig. 50). These consist of thick-walled cells nearly 

 as long as broad or a little longer and much swollen 

 in their middle part, the endophytic filaments thus 

 assuming a moniliform appearance (Fig. 51 c). The 

 length of the cells is about 12 — 14 fj. and the breadth 

 about 11 fjt. 



From this endophytic basal part the erect free 

 filaments arise (Figs. 50, 51 a, c). These are more 

 or less ramified through their whole length, in the 

 lowermost part on all sides, but higher up often 

 uniserially ; they taper only slightly towards their 

 summits. The filaments consist of cylindrical cells chætium hor- 

 which at the basal part are about 9—11 ^ broad morhi^mnoY. 

 and about 30 — 50 fx long, in the upper end 8 — 9 ^ flianient with 

 broad and about 60 fx long. The branches ramify sporangia. 

 repeatedly. All the branches are mostly rather straight. 



The cells contain a plate-shaped chromatophore (Fig. 52) 

 with a well developed pyrenoid protruding somewhat into the 

 interior of the cell. 



The sporangia (Figs, blh, 

 52) are mostly sessile but 

 some are pedicellate. They 

 occur as a rule upon the 

 lowermost cells of the fila- 

 ments seriate upon their 

 upper side, but now and 

 then also more scattered. 

 The sporangia are ob- 

 long-elliptic of shape, about 

 20—22 fx long and 10—11 fx 

 broad. 



Found once only in a 

 sheltered locality. 



St. Croix: Christiansteds 

 Lagoon. 



Fig. 53. Acrochsetium H]jpneæ Børgs. 

 Base of a plant. (About 300: 1). 



18. Acrochætium Hypneæ Børgs. 

 Chantransia Hypneæ Børgs., Some new or httle known West Indian 

 Florideæ, I (Bot. Tidsskr., 30. Bd., København 1909). 



4* 



