A very common plant in the North Atlantic, but strangely 

 misunderstood by early writers, who confounded it with Gracila- 

 ria confervoides ; a mistake which, with modern microscopes, it 

 would be impossible to fall into. It was first clearly defined as 

 a species, in the ' Flora Danica/ and was afterwards made the 

 type of a distinct genus, which in modern systems, represents a 

 separate family, widely parted from that to which 67. confervoides 

 belongs. The only resemblance between these plants is, that 

 both have long, and often simple branches. Neither in structure, 

 in substance, or in colour, is there any identity. 



The fructification, which was first described by Turner, has 

 been overlooked by many authors, and yet it is not unfrequently 

 produced. I have generally found an abundance of spores in 

 full-grown plants, gathered in the months of July and August. 

 They may most easily be elicited by compressing a small part of 

 a branch between two pieces of glass, and appear to exist in 

 equal numbers' in all parts of the plant. 



At Plate XVII. we have represented the only other British 

 species of Chordaria yet discovered. By comparing the figure 

 now given, with that plate, the differences and resemblances will 

 be readily appreciated. In younger plants of C. flagelliformis 

 the filaments of the periphery are exactly club-shaped ; in more 

 fully grown individuals, the terminal cellule is larger, and more 

 resembles that of C. divaricata than I formerly supposed. But 

 the difference in ramification is so great that there can be no 

 difficulty in discriminating between these species. 



Fig. 1. Chordaria flagelliformis : — of the natural size. 2. Part of a cross 

 section of the frond. 3. Longitudinal section of the same. 4. Filaments 

 of the periphery and spore. 5. A spore removed. 



