DUMONTIA. 147 



apices of the frond. Conceptacular fruit unknown. Name, 

 from furcula or furcilla, a little fork. The analysis of the 

 frond given in Phyc. Brit. Jigs. 3 and 4, is incorrect. 



1. F. fastigiata, Huds. ; Grev. Alg. Brit. p. 67, f. 11 ; 

 Hook. Br. Fl. ii. p. 283; Wyatt, Alg. Danm. No. 106; 

 Harv. Phyc. Brit. t. xciv. (figs. 3 and 4 incorrect) . Fucus 

 lumbricalis, E. Bot. t. 894. 



Bocks and stones between tide-marks, common. Perennial. Bearing fruit 

 in winter. Root a mass of stout fibres. Frond 6 12 inches high, terete, 

 simple at base, repeatedly dichotomous upwards, the apices fastigiate, the 

 axils acute. Substance between fleshy and cartilaginous. Colour brown- 

 ish purple, becoming much darker in drying. When in fruit the branches, 

 in the upper part, are swollen into a lanceolate pod-like figure, and are 

 found on dissection to contain beneath their surface a dense stratum of 

 dark brownish-purple, pear-shaped tetraspores, divided transversely into 

 four joints or sporules. The receptacles when ripe fall off, leaving the 

 branches truncated. In a state of the plant constituting Turner's var. /3., 

 the tips of the branches bear short, ovato-lanceolate, transparent, soft, pod- 

 like bodies, which appear to be imperfect attempts at fructification. These 

 Dr. Greville has sometimes observed to lengthen into healthy branches. 



X. DUMONTIA. Lamour. [Plate 20, A.] 



Frond cylindrical, filled with watery gelatine, tubular; its 

 walls membranaceous, composed externally of minute, round- 

 ish cells, internally of elongated cells, forming longitudinal 

 filaments. Fructification: 1, clusters of obovate spores at- 

 tached to the inner surface of the membrane of the frond : 2, 

 roundish tetraspores, among the surface cells. Name, in 

 honour of M. Dumont, a French naturalist. 



1. D. Jiliformis, Fl. Dan. ; frond tender, membranaceous, 

 cylindrical, pinnated with long, simple branches, which are 

 attenuated at each extremity. Grev. Alg. Brit. p. 165, 1. 17 ; 

 Hook. Br. FL ii. p. 308 ; Wyatt, Alg. Danm. No. 31 ; 

 Harv. Phyc. Brit. t. lix. Ulva purpurascens, E. Bot. t. 

 641. 0. crispata ; frond compressed, waved, curled or 

 twisted. Grev. Crypt, t. 240. 



Rocks and stones between tide-marks, common. Annual. Summer. /3. 

 in places exposed to tidal streams or currents. Frond generally undivided, 

 narrowed at each end, bearing numerous, alternate, simple or rarely forked 

 branches, similar to the primary ; of a membrano-gelatinous substance, 

 and yellowish, greenish, or dull purple colour, with intermediate shades. 

 A most variable plant. In some individuals the main stem is 8 18 inches 

 long, a line to half an inch in diameter, bearing numerous filiform 

 branches, 4 or 5 inches long. In others the stem is very short, 2 or 3 

 inches ; the branches 10 14 inches long, and of twice the diameter of the 



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