106 DICTYOTACE^.— ZoNARiA. iv. 



Root clotlied with entangled and curled woolly hairs, which extend a short way 

 from the base, covering from half an inch to an inch square of the lower part of 

 the frond. The frond, which eventually becomes a foot or more in length and 

 divided nearly to the base into many narrow lobes, originates in a sessile or nearly 

 sessile, broadly reniform, membranaceo-coriaceous lamina. This lamina has at 

 first a circumscribed margin, forming a somewhat cycloidal curve, and is nearly 

 undivided. "When it attains an inch or two in height, vertical slits, commencing 

 in the margin, extend downwards, dividing it in a pedate or palmate manner, into a 

 great number of narrow, wedge-shaped lacinise, placed side by side in digitate order. 

 These, as they grow, become flabeUate above, from the divergence of the rows of 

 cells of which they are composed, and are again cleft and re-cleft, until often the 

 orio-inallv reniform leaf becomes a bunch of narrow ribbons growing fi'om a central 

 point. In all these changes the apical margin remains truncate, and circumscribed 

 by a curved line. It is perfectly flat, not inroUed. Radiating strise, or inequalities 

 in texture, proceeding from the base upwards towards each lobe, are more or less 

 obvious in various specimens ; and faint concentric lines, paler than the rest of the 

 frond, are seen here and there crossing the lobes, at distances of a quarter to half 

 an inch. These are more evident on older and more divided specimens, though 

 they occur on the upper or newer portions of their fronds. The radiating longitu- 

 dinal bands or striee are sometimes very faint, and sometimes strongly marked. I 

 have not seen fructification on any specimen collected at Sand Key.* The colour 

 when growing is a dark olive, reflecting prismatic colours, chiefly vivid greens and 

 blues, from the striated surface. In fresh water a good deal of dark colouring 

 matter is given out ; yet in drying the frond becomes exceedingly dark. In this 

 state it adheres, but not very strongly, to paper, and shrinks very considerably. 



Not having seen authentically named specimens of Zonaria variegata, Ag., it 

 would be rash to say that that species may be only an undeveloped or small state of 

 the present. Some of my Sand Key specimens are so remarkably striated, or 

 marked with darker and paler longitudinal bands, and others so obscurely banded, 

 and there are such insensible gradations between the banded and unhanded 

 individuals, that I fear a character derived from these bands will not stand good. 

 If Z. variegata, then, be distinguishable ft-om our Z. lohata, it will probably be by a 

 character taken from the dififerent form of the sori, which are said to be " elliptical 

 and scattered" in that species. 



Plate VII. C. Fig. 1, plant of Zonaria lohata ; the natural size : fig. 2, small 

 portion of the summit of a segment, magnified, to show the surface cellules. 



* Tlie sori, on West Indian specimens, form dark lines at both sides of tlie pale, concentric band; 

 but, besides these linear sori, others of irregular form are scattered between the bands. 



