(10) 



an inch in length, and suddenly expanding into a broad flabelliform 

 frond with a roundish outline, obcuneate at the base, four to six times 

 dichotomou.sly divided, all the divisions linear oblong, but by their 

 forking, their outline is obcuneate ; the ultimate segments linear, with 

 rounded apices, pale and expanded when in fruit, afterwards more or 

 less erose when the fruit has dropped off. Structure densely cellular ; 

 central cells rather small, gradually diminishing in size towards the 

 surface, where they are excessively minute and closely packed, rendering 

 the frond somewhat firm and coriaceous. Colour, a fine permanent 

 brownish pink. Tubercles scattered on the segment, very convex, sessile ; 

 the pericarp thick, formed of the frond, and similar in structure, with 

 a narrow pellucid limbus, and containing a dense mass of angular 

 spores. Tetraspores forming dark coloured sori at the apices of the 

 segments, cruciate, sometimes imperfectly so, and only tripartite. 



This genus is now confined to those species having cruciate tetraspores. 

 These, moreover, generally distinguished among their former congeners by 

 thicker and more leathery fronds, and a darker and more sombre colour. 



This pretty species is said to be " not uncommon on the British shores, 

 from Orkney to Cornwall and Jersey ; " but we have never met with 

 it on the east coast. 



It is readily distinguished from the following by its smaller size, 

 oblong segments, fan-like fronds, brighter colour and thinner substance. 



To Phyllophora memhranifolia and Brodicei it has also at times a close 

 resemblance ; from the first it may readily be distinguished by the 

 narrow linear segments and brighter colour, but from the latter it is often 

 no easy matter to separate it, especially when without fruit, almost the 

 only diff"erence being the somewhat more cuneate form and almost 

 always more or less proliferous habit of P. Brodicei. 



The fruit affords a readier means of distinction, the tubercles being 

 seldom wanting in P. Proditei, and they are almost invariably terminal : 

 the proliferous elongations arising from among them, often in repeated 

 series. Generally the segments of this are much broader but not always 

 so, many specimens being as narrow as in P. Palmetta, but they are 

 rarely so deeply or s;) much divided. 



EXrLANATION OF PLATE LXIX. 



Fig. 1. — Rhodymenia Palmetta, natural size. 

 2. — Segment with tubercles. 

 3. — Section of tubercle. 

 4. — Spores from same. 

 5. — Segment with tetraspores. 

 6. — Section of same. 

 7. — Tetraspores from same. All magnified. 



