(82) 



any, subcylindrical, immediately expanding into the frond, which is flat, 

 regularly dichotomous from near the base ; segments linear, suberect, 

 from a quarter of an inch to three inches in length, the edges entire, and 

 the apices rounded, forked, emarginate, or entire. Fronds from three to 

 nine or twelve inches in length, and from one to four lines in breadth ; 

 the upper slightly narrower. Substance consisting of rather large 

 quadrate cells, disposed in linear longitudinal series, membranaceous, 

 very tender and delicate, scarcely adhering to paper. Colour, a pale olive 

 brown, sometimes dark brown towards the base. In our specimens of 

 variety j3 intricata the segments are gradually narrower upwards, the ulti- 

 mate ones almost filiform and patent ; all much twisted and entangled. 

 Fructification foiTning minute dark dots or sori under the whole sm-face 

 of the frond ; each sorus consisting of numerous spores or tetraspores, 

 attached by their apices and enveloped in a pellucid limbus, and, when 

 mature, divided in an obliquely cruciate manner into four sporules. 



We have not seen any specimens of var. ^ with fruit. Could its 

 slender and delicate habit arise from its having grown under shade or in 

 confined situations 1 The whole plant is much more delicate, the upper 

 segments being almost filiform, very much crisped and entangled, and 

 the apices often almost divaricate ; both varieties are said to gi-ow 

 together. 



Specimens also vary very much in colour, some being entirely of a 

 pale brownish olive, scarcely darker to the base, while others are pale 

 brownish olive at the apices, and dark brown or almost black towards 

 the base. 



The sori are often disposed to run into lines, but the lines are more 

 frequently longitudinal than transverse, the grouping is never so apparent 

 as those of the spores in the preceding species, and they extend almost 

 to the very base of the frond. 



EXPLANATION OF PLATE CLVIIL 



Fig. 1. — Dictyota dichotoma, natural size. 

 2. — Portion of frond with sorus. 

 3. — Portion of frond with scattered spores. 

 4. — Section of sorus. 

 5. — Sporea. All magnified. 



