122 CHORDARIACEiE. iv. 



many small potatoes. This genus, lumpy as it is, is closely allied in structure to 

 Ifesogloia, from which it is chiefly distinguished by the shapeless frond. The frond 

 in the latter group is branching, with a pinnate habit. A further advance in 

 structure is made in Chordaria, where the axis becomes very compact ; and in 

 Scytothamnus, a genus found at New Zealand, the frond attains its maximum of 

 structure. In that group the substance is as tough and leathery as it is among the 

 Fucacece, yet an appeal to the microscope shows a filamentous structure not 

 essentially differing from that found in Chordaria or Mesogloia. The genera Ela- 

 chista and Myrionema are a little different in structure from the other genera of 

 the order, and indicate a passage into Ectocarpacece. In them some of the 

 filaments composing the frond are free, or not enclosed in gelatine ; but as the 

 spores are lodged among the filaments which are compacted together into the base 

 of the fronds, I prefer retaining these genera in the present order. By Prof. J. 

 Agardh, ElacMsta is referred to Ectocarpacese, and Myrionema retained in Chordari- 

 acese, but both are so closely allied to each other, and also to Leathesia, that I am 

 unwilling to separate them. 



The spores of the Chordariaceaa are very generally obovate, obtuse at the apex 

 and narrowed to the base, and in many they taper so considerably as to become 

 almost club-shaped. They are enclosed in pellucid perispores, and attached to some 

 portion of the filamentous structure of the frond, generally to the filaments form- 

 ing the periphery or outer stratum. They are usually accompanied by paranemata. 

 In Ralfsia alone they form prominent, wart-like son, not unlike those of Stilophora 

 among Dictyotacete. The colour of the frond varies from a greenish to a brownish 

 olive, and is sometimes very dark. It is not much altered in drying. 



About forty-five species of this Order have been described from various parts of 

 the world. The majority are natives of the colder portion of the temperate zone, 

 both north and south; and some species, such as Leathesia tuheriformis and Chordaria 

 flagelliformis, are equally common in the Northern and Southern Hemispheres. 



I have found the gelatine of Chordaria JlageUiformis, extracted by allowing the 

 fronds to remain a day or two in fresh water, useful in causing small Alg£e, which 

 are not of themselves sufficiently gelatinous, to adhere to paper. It is however too 

 weak for any except very slender kinds. With this exception, none of the species 

 are used in the arts. 



SYNOPSIS OF THE NORTH AMERICAN GENERA. 



* Frond cylindrical, branching. 

 I. Chordaria. Axis cartilaginous, dense, solid (at length hollow in the centre) 

 Filaments of the periphery unbranched. 



