mentioned by Allioni. It does not appear to extend to the 

 Pacific, nor to be found in the Southern Ocean. 



It presents some varieties, chiefly distinguished by the greater 

 or less breadth of the frond, and the depth of the serratures. 

 I have chosen one of the most common states for illustration. 

 In the variety integerrimus of Turner, the marginal serratures 

 are very shallow, and sometimes obsolete, but always sufficiently 

 marked to prevent the species being mistaken. In his variety 

 latifolius, the upper branches are very much wider than the lower, 

 sometimes more than two inches broad, and remarkably rounded, 

 not unlike the webbed feet of some waterfowl ; and in Greville's 

 variety laciniatus, the serratures are very deeply cut, " and cleft 

 or lactate/' 



Messrs. Decaisne and Thuret, who first discovered the zoospores 

 above described, of which they have given a most interesting 

 account in the ' Annales des Sciences Naturelles ", divide the 

 Agardhian genus Fucus into several genera, of which F. serratus, 

 F. nodosus, F. canaliculatus, and F. tubercalatus respectively 

 are the types, and which they distinguish chiefly by the spores 

 containing eight, four, two, or one sporules ; a minute character 

 which accompanies some differences in natural habit, and might 

 be resorted to were the genus Fucus of great extent. But in so 

 small a genus it appears scarcely necessary to burden the science 

 with so many new names. 



To observe the zoospores in motion, fresh specimens, collected 

 in winter or early spring, having orange-coloured receptacles, 

 should be removed from the water, and left to dry partially. 

 As the surface dries, there will exude from the pores of the re- 

 ceptacle, drops of a thick, orange-coloured liquid, which, on being 

 placed under a microscope and moistened with salt water, will 

 be found to be composed of innumerable ant/ieridia, from which 

 will issue troops of zoospores, which, the moment of their libera- 

 tion, commence those strange animal motions which have so much 

 puzzled philosophers to reconcile with vegetable life. 



Fig. 1. Fucus serratus : — natural size. 2. Transverse section of the receptacle, 

 showing two conceptacles. 3. Spores from the same. 4. A cluster of anthe- 

 ridia. 5 .An antheridium containing zoospores, some of which have escaped : — 

 all magnified. 



