MARINE ALG^E OP THE SCOTTISH NATIONAL ANTARCTIC EXPEDITION. 75 



the Challenger from the same locality, and preserved in the herbaria of the British 

 Museum and the Royal Gardens, Kew. 



10. GYMNOSORUS VARIEGATUS, J. Ay. Two specimens without fruit. Off Brazil, 

 same locality as No. 3. 



Geographical Distribution. Warm Atlantic, Warm Pacific, Red Sea. 



11. STYPOPODIUM LOBATUM, Kiitz. Five 'specimens without fruit. Off Brazil, same 

 locality as No. 3. 



Geographical Distribution. Canaries, West Indies, Chatham Island. 



12. DICTYOTA DICHOTOMA, Lam, Off Brazil, same locality as No. 3. 



These plants show a variation from the ordinary type, inasmuch as the two branches 

 of the final dichotomy take on the narrow form characteristic of f. intricata. 

 Below this final dichotomy the plants are quite typical, and the change is a 

 sudden one. Mr Lloyd Williams has been so kind as to give us his opinion on 

 one of the specimens, saying that this development is probably the result of 

 unfavourable environment at a late stage of growth. He adds that he is able to 

 bring about such a change artificially in laboratory cultures. It is recorded as 

 having been taken at a depth of 36 fathoms a very deep habitat for a Dictyota. 

 But possibly it was caught floating free in the water ; and possibly it is a starvation- 

 form. When an alga is fixed, it thrives in the food-bearing currents which sweep 

 past it ; but if it should break off and float away in such a current, it would soon 

 exhaust the food in its neighbourhood, and would then be in risk of starvation. And 

 if carried down to an undue depth, it would pass out of the zone of optimum conditions 

 of light, C0 2 , etc. 



13. PHYLLOGIGAS SIMULANS, comb. nov. 



Syn. Lessonia grandifolia, A. and E. S. Gepp pro parte in Journ. of Bot., xliii., 1905, 

 p. 105, tab. 470, fig. 6. Lessonia simulans, A. and E. S. Gepp in Journ. oj Bot., 

 xliv., 1905, p. 425 ; National Antarctic Expedition, iii., British Museum (Natural 

 History), 1907, "Marine Algte," pp. 5-7, pi. ii., fig. 10. Phyllogigas grandifolia, 

 Skottsberg pro parte in Wissen. Ergebn. Schwed. Siidpolar-Exp., Bd. iv., Lief. 6, 1907, 

 pp. 63-69. 



Planta incompleta. Frons laminarioidea ut in P. grandifolia, stipite complanato 

 ancipite suffulta, simplex, lanceolato-linearis, longa, lata (12'5 cm. plusve), marginibus 

 iiitegerrimis. Laminae substantia pergamentacea vel coriacea, e stratis tribus composita ; 

 cellulis corticalibus nionostromaticis quadratis granuloso-obscuris ; subcorticalibus 

 oblongis parenchymaticis in circa 6-7 series dispositis ; medullaribus congestis elongatis 

 augustis strictis 9-10-seriatis tubulos perpaucos subinfuudibuliformes vagina e cellulis 

 parvulis composita vestitos foventibus. Ctetera desunt. (Figs. 6, 7.) 



Habitat. Scotia Bay, South Orkneys, near surface, April 1904, R. N. Rudmose 

 Brown. 



