numerous pores communicating with the immersed conceptacles or spore- 

 chambers. These latter are spherical, and contain numerous oblong, simple, 

 dark-brown spores, mixed with tufts of branching filaments bearing bright 

 orange antheridia. Colour, when young, a greenish olive, in age becoming 

 a rich brown. Substance very tough and leathery. 



One of the handsomest of the British Fucece and common on 

 all our shores. It is subject to little variation, except in size. 

 When growing in shallow water, or in tide pools near high water 

 mark, it becomes stunted in its habit, having the branches more 

 closely set, and bushy, and every part proportionably smaller and 

 narrower. This state constitutes the var. /3. of authors. 



The genus Halidrys, founded by Lyngbye, is well distinguished 

 from all other Fucece by the curious structure of its air-vessels. 

 These compound air-vessels are confined to the present individual, 

 and to the beautiful Facus osmundaceus of Turner, a native of the 

 West coast of North America. In this latter species the struc- 

 ture is slightly different, and the vesicles are much constricted at 

 the joints, like strings of beads. The whole habit, however, is so 

 very similar to that of our H. siliquosa, that I cannot but con- 

 sider it as properly a member of the same natural genus. 



Fig. 1. Haliduys siLiauosA ; Portion of a branch : — the natural size. 2. Lon- 

 gitudinal section of an air-vessel. 3. Transverse section of a receptacle, 

 with its immersed conceptacles, containing spores and antheridia. 4. Spores : 

 — all more or less maqnil 



