VALONIACEiE. 41 



Order III.— YALONIACE^. 



Valoniece, in part, Kutz. Sp. Alg. p. 507. Anadyomenece, Didyospheriece, and 

 part of Codiece, Kutz. I. c. Siphonece^ in part, Aixct. alior. 



Diagnosis. Green marine Algte, naked or encrusted with carbonate of lime, with 

 fibrous roots. Frond polymorphous, formed of large vesicated cells filled with watery 

 endochrome ; either consisting of a single cell, or of several united into filaments, or 

 into net-works or membranous leaf-like expansions. 



Natural Character. Root in most cases well developed, and consisting of a plexus 

 of tough fibres, forming a mat, and either penetrating the sand or grasping firmly to 

 the rock or stones on which the plant grows. Frond very variable in form, and in 

 complexity of structure. In Valonia the whole frond, in some species, consists of a 

 single vesicated cell, which is often of large size, upwards of an inch in length, and 

 three-quarters of an inch in diameter, filled with a thin, watery endochrome. In other 

 species of that genus, several such cells are strung together so as to form confervoid 

 branching filaments. In Dictyosphceria, a number of large globose cells cohere toge- 

 ther in a single stratum, and thus form a tessellated or honey-combed membrane. In 

 Anadyomene, the membranous expansion is formed in a difierent manner, namely, by 

 the lateral cohesion and anastomosis of a branching filament ; and in Mierodictyon, a 

 network is formed in a similar way, the difierence from Anadyomene being, that the 

 branches of the generating filament stand apart, leaving open spaces between their 

 anastomosing ramuli. A further advance in structure occurs in Penicillus, where the 

 frond has a dendroid habit ; tlie trunk of the treelike body being composed of branch- 

 ing, unicellular filaments like those of a Codium, and the head of confervoid, articulated 

 filaments like those of Valonia. This spongy caudex, or trunk, appears to me to be 

 merely an exaggeration of the rooting processes, common to most plants of the family. 

 A more definite stipes, or true stem, is found in Chamcedoris, Apjohnia, and Struvea, 

 the most highly organised genera of the Order, and those which connect it with the 

 DasycladecB. In these the stipe is monosiphonous, and is developed nearly to its full 

 size before any part of the capitulum makes its appearance. In the early stage these 

 plants are not to be known from the simple Valonice, and like them consist of a single 

 cell rising from a branching root. 



In this description of the fronds of the Order I omit the curious plant which will be 



G 



