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



47 



grows upwards, while from the lower endo- 

 phytic filaments growing downwards are 

 produced (Figs. 44, 45 c and d). The last 

 mentioned fdaments grow downwards round 

 the assimilating filaments of the Liagora 

 upon which the spore has germinated. 

 They do not penetrate into the cells of 

 the host plant but only into the mucilage 

 and chalk incrustation found between the 

 filaments. 



The main filament arising from the 

 germinating spore remains in most of the 

 specimens undivided in the basal part 

 (Fig. 45 a), but specimens were found in 

 which a single or few branches were given 

 off from near the base. In some of the 

 more adult specimens erect filaments were 

 found growing up from cells in the des- 

 cending filaments (Fig. 44). On one occa- 

 sion a descending filament was found 

 growing out from a cell near the base 

 of the erect filament (Fig. 44). The cells a, haMt of erect, ramified 



in these are about 8— 11 « broad and their ^ament with sporangia 



•^ 0, part of plant with 



length about 35//. - - - 



When the erect filaments have grown 



long enough to become free of the Liagora 



they begin to branch more freely. 



The branches issue from the upper end of 



each cell mostly in an uniseriate manner; these 



branches bear again branches arranged secundly. 



Towards their apex the branches are undivided 



tapering somewhat becoming about 8 fj. thick, at 



the same time the chromatophores are not so 



well developed. 



The chromatophore is parietal (Figs. 44, 46) 



with a large pyrenoid. 



The sporangia are broad oval and mostly 



pedicellate (Figs. 45 a, b, Fig. 46), placed upon 



FigACy.Acrochæ- g^ort secund branchlets beins: seriately arranged 



liuin comptum o j » 



nov. spec. Part upon the upper, inner side of the branches. The 



°^.,,^ ^'^^'"^•'^* branchlets are as a rule one-celled and bear 

 with sporangia. 



(About 4(1(1:1). mostly a single sometimes two sporangia. Sessile 



Fig. 45. Acrochætium 

 comptum nov. spec. 



sporangia, c and d, bases 



of plants, (a, about 



50 : 1 ; b, 250 : 1 ; c and d, 



150: 1). 



