Bd. IV: 5) ANTARCTIC AND SÜBANTAKCTIC CORALLINACE.E. 



7. Lithothamnion heterocladum Fosl. 



Vidensk. Selsk. Aarsber. (Bot. Saml.) 1904 (1905). 



f. gracilis FoSL. 



1. c; tab. nostr. i, fig. 16 — 22. 



Syn. Lithoth. squarrulosum Heydr. Lithoth. Mus. Paris p. 541 



Though as yet only sterile specimens of this alga are known, I think it almost 

 unquestionable that it represents an independent species of the genus Lithothamnion. 

 It was probably first found by the Challenger-E.xpedition and was referred by DiCKIE ' 

 to Melobesia calcarea. In habit it no doubt very nearly approaches Lithoth. calca- 

 reiini, and so it does also as to structure, though some scars I have found from 

 conceptacles emptied seem to suggest that in the latter respect it is more closely 

 connected with L. i-ugosinn. I have even seen specimens of these species, the ty- 

 pical forms of which are widely different, much approaching to each other also in 

 habit. It is, therefore, not improbable that L. heterocladum should be a species 

 proceeding from L. nigosnm rather than from L. calcaremn. 



There are two forms of the species, a coarser one, f. crassa with the branches 

 about 3 — 4 mm. thick, and a finer one, f. gracilis, whose branches are about 2 — 4 

 mm. thick (PI. i, fig. 16 — 22). The former comes very near to Lithoth. pulchrum, 

 but is smaller. Cp. Siboga-Exp. LXI. pi. IV. On the other hand, f. gracilis ap- 

 proaches Lithoth. australe f. tualeusis and f. bracht ata. Cp. 1. c. pi. II. 



Lithoth. heterocladum occurs in the sublitoral region. It is certainly alleged to 

 have been found in the litoral region in the Beagle Channel, but a couple of speci- 

 mens collected in this locality are likely to have been washed up from the upper 

 parts of the sublitoral region. At the Observatory Island it occurs in a depth of 

 about 14 fathoms, associated with LJthoth. rugosum and other species, but also here 

 apparently in no great numbers. DiCKlE on the contrary states 1. c. : "It forms 

 dense beds in Isthmus Harbour, Straits of Magellan, and was dredged in 8 fathoms." 



Area: Patagonian Channels: Isthmus Harbour, f. valida (Challenger-Exp.); 

 Smyth Channel, Puerto Bueno, f. valida (v. Paessler); Smyth Channel, Long Is- 

 land, f. gracilis (MichaelSEN); Beagle Channel, f. gracilis (Skottsberg); Observa- 

 tory Island near Staten Island (Skottsberg). 



' Dickie. Supplemenial Notes on .\lgx collected by 11. N. Moseley, M. \.. of 11. M. S. '-Ch.-illen- 

 ger", from various localities. 4. Algœ from Port Louis, Falkland Islands, and Magellan-Straits. — Journal 

 Linnean Society. Bot. Vol. 15. (1875 — 77). P.ig. 446. 



Schwedische Südfolai- Expedition içoi — içoj. ^ 



