Collins and Howe: Species of Halymenia 171 



This species seems to be fairly common in Bermuda. Its 

 favorite habitat is the walls of narrow deep clefts in the shore 

 cliffs, such as are found between Tucker's Town and Walsingham. 

 Here it grows from a little below low-water mark down at least to- 

 a depth of two or three meters, usually as single separate plants 

 rather than in dense tufts. It seems to thrive best where much 

 shaded. In an unattached condition it occurs also among man- 

 grove roots, as in the vicinity of Hamilton. These loose fronds are 

 darker in color, firmer in texture, and less adherent to paper when 

 dried under pressure than are the attached forms. There is much 

 variation in the form of the frond ; the primary form seems to be 

 orbicular and plane with a slightly developed stipe. Rapid marginal 

 growth of the frond results in ruffles and plications, and when these 

 are well developed the plant has somewhat the aspect of Porphyra 

 amplissima in miniature. In color and habit it is often suggestive 

 also of certain conditions of Callymenia reiiiformis, from which, 

 however, it differs markedly in structure. Proliferous growth is 

 common; the proliferations are sometimes sessile but are oftener 

 stipitate, the stipe terete or flattened, in the latter case with or 

 without an obvious costa, which may be continued into the base 

 of the main expansion. In the older plants, under certain con- 

 ditions of growth, the basal stipe, terete or flattened, may branch 

 and form a matted subrhizomatous complex from which individual 

 fronds arise, these usuallj^ orbicular or cuneate, or sometimes 

 cordate from a cuneate base. An important character of this 

 species is the presence, in the medulla, of conspicuous stellate 

 ganglia more or less similar to those exhibited by the type speci- 

 men of Halymenia floridana J. Ag. and by Sebdenia heteronema 

 M. A. Howe.* These may be easily observed through the cortex 

 by transmitted reduced light under low-power lenses without the 

 use of any staining reagents; however, their protoplasts have a 

 peculiar aflfinity for haematoxylin stains and they may be differ- 

 entiated with remarkable distinctness by overstaining with prepar- 

 ations of haematoxylin and afterwards partly decolorizing. The 

 nodes of the ganglia are irregularly stellate or subglobose ; from each 

 of them radiate three to ten coarse rather rigid and straight taper- 

 ing filaments with dense homogeneous refringent contents ; in the 



* Mem. Torrey Club 15: 163-165. pi. 58. 1914- 



