48 



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



sporangia also occur often rather numerous especially in the upper 

 part of the plant. The diameter of the sporangia is about 11— 

 lA/jL, the length about 18//. 



This species has been found upon Liagora pinnata. 



St. Croix: White Bay. 



16. Acrochætium Avrainvilleæ nov. spec. 



Thallus cæspitosus usque ad 1 mm altus. Pars basahs ex 

 interiori parte plectenchymatis hospitis emergens, ex filis brevibus 



in filis hospitis externe repentibus 

 composita. 



Tola planta a basi ad apicem 

 sensim attenuata. 



Fila erecta, a basi simplicia, in 

 superiori parte ramosa, ramis multi- 

 laterahbus, rectis, plus minus ramosis 

 instructa. 



Gellulæ cylindricæ, in parte basali 

 ca. 9 fi latæ 33// longæ, ad apicem 

 versus ca. 4/« latæ 50// longæ, chro- 

 matophorum parietale, pyrenoide late- 

 rali instructum continentes. 



Sporangia sessilia aut interdum 

 pedicellata, sparsa aut pauca seriata, 

 oblonga, 11 /j. lata, 22 jm longa. 



This plant was found upon an 

 old specimen of Avrainvillea nigricans. 

 The basal part of it was fixed to a 

 filament of the host plant lying rather 

 deep in the cortical plectenchyma 

 (Fig. 47 a) ; on account of its very loose texture the Acrochætium 

 has no difficulty in growing out through it, and as I have only 

 met with two specimens of it in all I dare not deny the pos- 

 sibility that the Acrochætium might be found quite epiphytic 

 upon the external filaments of the host. 



The basal part consists of short, creeping filaments attached 

 to the surface of the filaments of the host plant; they consist 

 of proportionally short and thick-walled cells. 



From the cells in the middle of the basal filaments the erect 

 ones are given off (one or more). 



At their base the erect filaments are unbranched (Fig. 48) ; 



Fig. 47. Acrochætium Avrain- 

 villeæ nov. spec, a, filaments 

 of Avrainvillea nigricans with 

 the basal part of the Acro- 

 chætium. b, base of the same 

 plant more magnified. 



(a, about 40:1; b, 700:1). 



