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



347 



second or third cell in the filaments, and filaments occur which are 

 not branched at all. Nienburg*), in his paper on the construction 

 of the thallus of the Delesseriaceæ, has pointed out (1. c, p. 205, 

 6, figs. 43, 44) that we have two principal ways of ramification in 

 this family. Of these our plant agrees with the Hypoglossiim-tj^^e as 

 found in Delesseria Hypoglossiim. 



As I have already mentioned in my paper quoted above, tetra- 

 sporic as well as antheridial and cystocarpic plants were found in 

 my collection. 



The tetrasporangia 

 (Fig. 341 d) occur close 

 to the midrib, symmetri- 

 cally arranged on both 

 sides of it. Their develop- 

 ment begins at about the 

 middle of the leaf and 

 continues upwards, the 



tetrasporangia being 

 younger and younger to- 

 wards the summit. 



The antheridial stands 

 (Fig. 342 A) are placed on 

 both sides of the midrib 

 of the leaf forming low, 

 dense cushions. They are 

 arranged rather regularly, 

 generally following the 



main filament in each of the branch-systems of which the leaf 

 consists, leaving in this way the side-branch bare, but it happens 

 that some of the cells in these, too, are covered with antheridia, 

 some larger tufts being formed in this way. The arrangement of 

 the antheridial stands bears rather a close resemblance to 

 that found in Delesseria riiscifolia, cp. Buffham**). The 

 cystocarps (Fig. 343) are urn-shaped and issuing from the midrib 

 of the leaf. 



Fig. 343. Delesseria tenuifolia Harv. 



A nearly ripe cystocarp. 



(About 80:1). 



*) Nienburg, W., Zur Keimungs- und Wachstumsgeschichte der Deles- 



seriaceen. (Botanische Zeitung, 1908). 

 **) Buffham, P. H., On the antheridia, etc. of some Florideæ (Journal 

 of the Quekett microscop. Giub., vol. V, ser. II, 1893, p. 6, pi. LXIV, fig. 25). 



