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curved towards the centre of the sorus; they are 3—5-celled, 6 broad at the base, 
upwards a little thinner. The sporangia are born of a stalk cell as in the other 
species; they are 26—32 » long, 21—24 » broad. After the evacuation, a new spor- 
angial cell is cut off from the stalk cell within the empty sporangial wall. 
I agree with Hrypricn and CoLLiNs in retaining the species in the genus 
Rhododermis. When occurring in its disc-shaped form it resembles R. elegans so 
much that it differs only in the dimensions of the cells of the frond, and there 
but slightly. 
The species grows on the leaves of Zostera produced in the foregoing year, 
but also in shed leaves. It has been met with in the months of April to August, 
in all these months in disc-shaped and inflated specimens and with sori. In April 
the sporangia were yet undivided; in May and June unripe and ripe sporangia were 
met with, in July and August ripe sporangia were found, but also emptied and 
regenerated ones. The species has also elsewhere been found with sporangia in 
spring and summer. 
Localities. Lf: Repeatedly at Nykøbing (!, C. H. Ostenfeld). — Kn: In several places at Hirs- 
holmene (!, Ostenfeld, Henn. Petersen); Frederikshavn, Busserev, and between Borrebjergs Rev and Marens 
Rev; ZL, S.E. of Nordre Ronner, 6,5 m and 11m. — Sa: Off Risskov at Aarhus. 
Fam. 8. Hildenbrandiaceæ. 
The family of the Hildenbrandiaceæ, established long since (Comp. RABEN- 
HORST, Fl. eur. Alg. III, 1868, p. 408) and still maintained by Scumirz in 1882 (Hauck, 
Meeresalgen, p. 37), was later abandoned by this author as the presumed cystocarpia 
of the genus Hildenbrandia had proved to be conceptacles of tetrasporangia, and he 
therefore ranged this genus under genera incertæ sedis in 1889 (Flora, p. 22). In 1897 
SCHMITZ and HAUPTFLEISCH range it as a dubious Corallinacea. On the other hand 
DE Toni places it under the Squamariaceæ in a subfam. Hildenbrandtieæ (Sylloge 
Alg. Vol. IV, sect. IV 1905, p. 1713). I think it better to consider the genus as a repre- 
sentative of a particular family intermediary between the Squamariaceæ and the 
Corallinaceæ. Although the sexual reproduction is unknown, the family is sufficiently 
characterized by the want of incrustation with lime of the frond, by the presence 
of immersed conceptacles of sporangia, and by the oblique divisions of the spor- 
angia. The conceptacles resemble those of the Corallinaceæ but develop in another 
way, as will be mentioned below. Oblique divisions of the sporangia do not occur 
in the Corallinacew, but are characteristic of several Squamariacee. 
Hildenbrandia Nardo. 
1. Hildenbrandia prototypus Nardo. 
Nardo, De novo genere Algarum cui nomen est Hildbrandtia prototypus. Oken’s Isis 1843, p. 675; Hauck, 
Meeresalg. p. 38. 
Zonaria deusta Lyngbye, Hydr., 1819, p. 19 ex parte; cfr. notula. 
