3° 2 



F. BORGESEN 



The mutual arrangement of the branchlets and branches is seen in Fig. 42. 

 This shows that the branchlets are, as a rule, developed from every fourth 

 segment; the next has a branch and the branches alternate on the right and 

 left side of the thallus. But it happens that the branchlets are developed 

 from ever)'" third or rarely from every second segment. The branchlets are of 

 rather variable length; in some specimens I have counted up to 50 segments. 

 The segments are longest in the middle of the branchlets, shorter near the 

 base and summit. The diameter of the branchlets is about 50 jj.. The tricho- 

 blasts are as a rule poorly developed. 



On Zonaria variegata I found some few fragments of an other form, both 

 cystocarpic and tetrasporic, but unfortunately no male plant. 



Of the female plant Fig. 43 gives an illustration; it is much more robust 

 than the sterile one from Valonia. It also differs from this by the scarce 

 development of branches, which generally are arranged without any order. 



Fig. 43. Herposiplionia tenella{C. Ag.) Naeg. 9. a part of creeping plant, c. °°/ij b growing apex 

 ot same, c. 750 /j; c voting cystocarp, c. m /i. 



The trichoblasts are well developed in the female plant. The cystocarps are 

 formed in the second segment of the trichoblast, the lowermost becoming 

 polysiphonous. The form of the young cystocarp (Fig. 43 c) very much resembles 

 what I have found in LopJwsiphonia cristata (comp. my fig. 432 1. c). The 

 trichogyne is thick and comparatively short. The ripe cystocarp is urn-shaped 

 with a short broad neck; it is about 550 p. long and 460 ;j. broad. 



The tetrasporic specimens have longer and much more slender branchlets 

 than the female plant; in the mutual arrangement of the branchlets and branches 

 they agreed with the plant found on Valoiia. The tetrasporic branchlets are 

 about 60 {A thick and 1,5 mm long. 



Area of distribution: Mediterranean Sea, Morocco, West Indies, Malayan 

 Archipelago, Easter Island. 



A small piece of a plant with 1 1 pericentral cells may perhaps belong to 

 H. subdisticha Okamura (Bot. Mag. XII, 1899, p. 11, pi. I figs. 12—14). It 

 resembles the figures quoted, but being sterile and lacking growth points it is 

 insufficient for a safe determination. 



