120 GELIDIACEJ5. 



V. 



a half ounce letter, but I fear the differences indicated do not amount to specific 

 characters ; for I find, among some hundred specimens which have passed through 

 my hands, great diversity in diameter and in the comparative obtuseness of the 

 spines ; and the colour depends very much on the longer or shorter exposure to 

 alternate sunlight and rain. Should, however, future observations show that I 

 have confounded two species, tlie present will, I hope, bear the name of Dr. Wurde- 

 man, its estimable discoverer at Key West. 



Plate XXIV. Fig. 1. Eucheuma isifojvne, the natural size. Fig. 2, part of a 

 branch with conceptacles ; jig. 3, section of a conceptacle ; Jig. 4, spore-threads ;_y?^. 

 5, semi-section transversely of a branch ; fig. 6, a longitudinal section through the 

 same ; more or less magnified. 



in. SOLIERIA. J. Ag. 



Frond cylindrical, subcartilaginous, succulent, fruticose, composed of three strata ; 

 the axis (or medullary stratum) consisting of longitudinal, anastomosing filaments; 

 at first few, afterwards densely interwoven ; the intermediate stratum of several 

 rows of roundish cells, of which the inner are large, the outer successively smaller 

 and more angular ; the cortical of two or three rows of minute, coloured cellules. 

 Conceptacles immersed in the axial region of the branch, but prominent to one side, 

 the walls formed of a dense plexus of filaments dei'ived from the axis ; placenta 

 fibrocellular, central, suspended in the cavity by slender filaments connected with 

 the walls: sjoores pedicellate, pear-shaped, covering the whole surface of the placenta. 

 Tetraspores transversely parted, [zonate) dispersed among the peripheric cellules of 

 the branches and ramuli. 



The frond is cylindrical, irregularly branched, of a somewhat tender substance, 

 crisp when quite recent, but soon becoming flaccid. When young the axis is ex- 

 ceedingly lax, and the branches are almost hollow, the axial region being occupied 

 by a watery gelatine, through which a few distant, longitudinal, anastomosing fila- 

 ments are dispersed. Toward the base of the frond and in older specimens the 

 axis is much more dense, and finally, when the growth is fully matured, it becomes 

 a compact plexus filling up the vacant space, and solidifying the branch. The 

 intermediate stratum, or the region between the axis and coloured periphery, in like 

 manner, becomes more compound with age, the addition of new cells being made 

 on the outside ; and the cells of the innermost row are always of much greater 

 diameter than those of the exterior rows. The periphery does not undergo much 

 change. The conceptacles appear externally like obtusely conical tubercles with a 

 dark coloured coi-e, scattered profusely over the branches of fertile specimens. A 



