VALONIACE^. 49 



The frond in this genus is thin and membranous, and at first view resembles that of an 

 C/foa, except that it is traversed everywhere by branching veins. When more closely 

 examined it is easily pei'ceived that the membrane is wholly formed by the anastomosis 

 and lateral cohesion of the branches and ramuli of a much branched, articulated, con- 

 fervoid filament, composed of large, oblong cylindrical cells ; as more fully detailed in 

 the subjoined description. As Professor J. Agardh remarks (Alg. Medit. p. 24), it is 

 nearly related to Valonia, from which it differs chiefly in the lateral cohesion of the 

 branches of the generating filaments, and to which it bears the same relation that 

 Codium does to Vaucheria. It is still more nearly related to Microdictyon, where the 

 fronds form an open network. 



1. Aii XDYOKESE flabellata, Lamour. ; frond flattish or undulate, the veins multipar- 

 tite. Lamour. Pol. Flex. p. 365, tab. 14, Jig. 3. Bory, Fl. Mor. t. 41, jig. 5, Kutz. 

 Sp. Alg. p. 511. A. stellata, Ag. Sp. Alg. \,p. 400. (Tab. XLIV. A.) 



Hab. Key West, on tidal rocks, common. Dr. Wurdeman, W.H.H., Prof. Tuomey. 

 (v. V.) 



Root consisting of a mat of branching, articulate, confervoid filaments, emitting erect 

 branches which develope into flat, flabelliform, membranous fronds. Fronds tufted, 

 1-4 inches long and as much in width, rigidly membranaceous, shortly stipitate ; the 

 stipes uni- or pluri-cellular ; lamina at first flabelliform and entire, afterwards undulate 

 and more or less deeply lobed at the margin ; wholly composed of radiating, multifid, 

 branching, confervoid filaments, whose distichous branches closely cohere throughout, 

 and whose ramuli as constantly anastomose and coalesce. In other words, the membrane 

 is composed of longitudinally seriated, cylindrical cells, several series radiating from the 

 base toward the circumference in a flabellate manner, and dividing and subdividing 

 digitately throughout the whole length of the series ; each cell emitting from its sum- 

 mit 5-7 or more similar cells, which in their turn put forth another series, and so on. 

 In this way the frond increases in length. It is widened by the gradual evolution of 

 other cells formed along the sides of contiguous parallel cells in a pinnate order. At 

 first these lateral or transverse cells are very minute and placed opposite each other. 

 They gradually lengthen, anastomose and coalesce, and at length form a reticulated space 

 of a narrow wedge-form between each pair of tubular, longitudinal cells. The cuneate 

 space looks like a membrane, but is really constituted of closely placed, transverse bars, 

 leaving narrow slits between them, as may be readily seen by examining a dried speci- 

 men when the substance shrinks. In a moist state, by the swelling of the cells, the 

 slits close up, and the frond appears as if continuously membranous. The tubular, 

 longitudinally seriated cells, or those that form the veins and nerves of the frond, seem 

 to continue to lengthen during the whole growth of the lamina ; they are short in 

 young plants, longer in others, and in old plants are many times longer than their 

 diameter. The cell-wall in these cells is thick and tough, and when viewed under a 



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