Ser. MELANOSPEEME^E. ( 95 ) Fam. DIGTYOTE^. 



PUNCTARIA TENUISSIMA.— 6^/m 



Gen. Char. — Frond gelatinoso-membranous, flat, without midrib. Fructification exter- 

 nal, scattered over the whole surface of the frond, consisting of roundish ovate 

 spores, mixed with short, articulated, club-shaped filaments, and forming little 

 tufts or sori. Name from ^JMwrfwm, "a point or dot," in allusion to the dots of 

 fructification. 



PuNCTARlA tenuissima. — Frond very tender, sublinear, attenuated to a 

 slender base, and to an obtuse point at the summit. 



PuNCTARiA tenuissima. — Grev. Alg. Brit. p. 54 ; Hoolc. Br. Fl. vol. ii. p. 279 ; 

 Harv. P. B. plate 248 ; Harv. Man. p. 42 ; Harv. Syn. p. 37 ; 

 Atlas, plate 13, fig. 51 ; Harv. N. B. A. part 1, p. 115. 



PtJNCTAKiA undulaia. — /. 0. Agarclh, Sp. Gen. Alg. vol. i. p. 72. 



Ulva plantaginifolia. — Lyngh. p. 31, t. 6 (fide /. Ag.). 



DiPLOSTROMiUM plantagineum. — Kutz. Phyc. Gen. p. 298. 



Hab. — Parasitical on Chorda filum, &c., near low-water mark. Annual. Summer. 

 Not uncommon. 



Geogr. Dist. — Atlantic shores of Northern Europe ; Baltic Sea ; North-west coast of 

 France ; North America. 



Description. — Root, a minute disc. Frond scarcely stalked, at once 

 widening into a naiTOW sublinear or linear-ovate frond, gradually taper- 

 ing from a point a little above the base into a long, acuminate, obtuse 

 point; occasionally the apex is obliquely truncate or suddenly acuminated 

 into a short point ; the margin more or less waved or curled, and occasion- 

 ally furnished with a few distant teeth. Structure consisting of rather 

 large quadrate cells. Substance very delicate, submembranaceous, rather 

 firmly adhering to paper. Colour, a pale yellowish olive. Fructifica- 

 tion : the only appearance of anything analogous to this which we have 

 seen, is numerous small roundish granules, sometimes single, sometimes 

 in pairs, but more frequently collected in small groups, and scattered 

 over the whole surface of the frond. These seem to be identical with 

 what are described in Phyc. Brit, under the last species as antheridia, 

 which they may either be or the spores in a nascent state. 



This pretty delicate species is by no means uncommon; at least we 

 have sometimes met with it in considerable plenty, while at other 

 times, in the same locality, scarcely any could be found. Indeed it 

 seems not only of uncertain appearance, but very evanescent in its 



