which w<- thinl the ancestry ol Rhipilia. For the lateral 



ivhich, emitted in vigorously growing specimens ol /. minima 



in filam nd and, creeping over and among them, serve to hold them 



much remind u laculiferous branchlets of Rhipilia. We regard F. minima 



'u in ui Rhipilia out of the primitive Chlorodesmi 

 ■>n p. - 

 In the filaments are looselj interwoven and bear short pseudo-lateral branch 



. which are terminated by digitate tenacula. rhese tenacula ar< either 

 to adjacent filaments, thus adding strength to the loosely felted 

 .1 method i>t' connection l>y means of tenacula is unknown in both Udotea and 



Many of the tenacula remain unattached and il occurs to us thal some of them may 



Ij .ut as organs for thrusting asunder the filaments of the feltwork, thereby 



ling an easier passage for water to stream through the open network and a freer a 



for I l >therwise these unattached branchlets appear to have no function. This open-work 



structure, what similar in function to that found in Microdictyon^ Struvea, Haloplegma, 



Mar • ti\, is most obvious in R. oritii/alis, in which species the tenaculiferous 



branchlets are longest see fig. 136). In R. tenaculosa the tenacula are so abbreviated that 



bind the filaments into a much closer weft, producing a stronger frond, but allowing less 



lom for the percolation of water through it. In R. tomentosa f. typica the frond is thicker 



and firmer; its strength is largely derived from the felting together of its filaments, resulting 



in a spongy habit likc that of Avrainvillea. 



Rhipilia is distinguished l>y the frequent absence of constriction at the base of its branches 

 and branchlets. The filaments of Rhipilia show the characteristic stoppers (or introrse annular 

 thickenings of the wal! of the filament) common to so many of the Siphoneae. (Fig. 128). 



Rhipilia Kiitzi 

 Tab. Phyc. VIII. 1858. p. 12. 



Thallus green, without calcareous incrustation, stipitate or subsessile; sometimes arising 

 from a horizontal rhizome ; frond either cuneato-flabellate, flabellato-rotundate or excentrically 

 sub-infundibuliformi-peltate, thick to very thin, sometimes zonate, ecorticate, filaments of frond 

 cylindrical, here and there slightly and irregularly thickened, thin-walled, collapsing when dried, 

 laxly interwoven, repeatedly dichotomously branched, branches often not constricted at 

 their base; many of tli<: branches, remaining more or less short, assume a lateral position and 

 ure terminated by a tenaculum or crown of 2 — 6 short processes, which is either applied to 

 filament or remains free. 



1. Rhipilia tomentosa Kützing 



Phyc. VIII. 1 S ; s . p. u. tab. 28 I. 



'ra laetevirens Crouan ex Mazé & Schramm, de la Guadeloupe ed. II. 



P 



