HOWE AND HOYT: MARINE ALGAE FROM BEAUFORT, N. C. II7 



in 131^-14 fathoms of water on reef about 23 miles ojff shore from 

 Beaufort, North CaroHna, August 11, 1914, by Lewis Raddiffe. 

 The endozoic parts are embedded principally in the inner layers 

 of the perisarc of the stalks, stolons, and occasionally the hyd- 

 ranths. 



Acrochaetium infestans doubtless finds its nearest ally in Chan- 

 transia endozoica Darbish. (Ber. Deutsch. Bot. Ges. 17: 13-17. 

 pi. I. 1899), originally described as occurring in a bryozoan, 

 Alcyonidium gelatinosuni, on the southern coast of Ireland, and 

 since reported also from Denmark by Rosenvinge (Kgl. Danske 

 Vidensk. Selsk. Skrift. VII. 7: 128. 1909). From this species, 

 as described and figured by Darbishire, Acrochaetium infestans 

 appears to differ in having the diameter of both immersed and 

 exserted filaments averaging about one half as great, in the much 

 more tortuous, more irregularly branched interior filaments, the 

 more curved and irregular cells of which are actually, on the 

 average, two or three times as long, and relatively to their width, 

 four to six times as long, as in the European species. The spor- 

 angia of Chantransia endozoica, as figured by Darbishire, are only 

 slightly broader than the subtending sterile cells; in A. infestans, 

 the mature sporangia are nearly twice as broad as the subtending 

 cells. Darbishire noticed one possible hair in his C. endozoica, 

 but was not sure that it really belonged to the organism in question. 

 In Acrochaetium infestans, the larger exserted filaments commonly 

 show hairs of remarkable length. 



Acrochaetium infestans is associated with various mostly smaller 

 algae that penetrate the hydrozoan little if at all. The more 

 common and conspicuous of these are Acrochaetium affine and a 

 closely adherent filamentous blue-green {Phormidium sp.?), the 

 latter with trichomata 0.75-1.5 /z in diameter and cells mostly 

 1-2 (^-3) times as long as broad. The interior parts of the 

 Acrochaetium infestans are, in our formalin-preserved material at 

 least, so nearly colorless, and the plant in general is so small that 

 it might easily escape observation if one did not happen to empha- 

 size its existence through the use of differential stains. By 

 applying iodine (potassium-iodide solution) the little plant is 

 thrown into bold relief, its protoplasts becoming violet-red or 

 brownish crimson, while its host becomes a light yellowish 

 brown. 



