52 FUCACE^. IV. 



puscle is always in front ; while the cilium, rising from the coloured granule, 

 trails behind like a tail. 



Messrs. Decaisne and Thuret, from whose memoir (in Ann. des Sc. Nat. 1845, p. 5 

 et seq.) this description is mostly taken, point out the strong analogy between these 

 vivacious corpuscles of the Fucacem and the so-called spermatozoa of the Characete, 

 Mosses, and Hepaticse, and argue from this similarity of structure a similarity of 

 function. They are, therefore, of opinion that the corpuscle-bearing cells are 

 properly organs of a similar nature to the antheridia of other cryptogamic- plants ; 

 and not, as is supposed by Agardh, analogues of the sporidia of the lower Alg^, 

 and like them capable of germination. From my own investigations, I am disposed 

 to ao-ree with the opinion which regards them as male organs. They may readily 

 be seen with the higher powers of the compound achromatic microscope ; and are 

 easily found in the ordinary shore Fuci, (Fucus vesiculosus and F. nodosus), in 

 winter or early spring, on specimens bearing bright yellow or orange coloured 

 receptacles. Some of the most deeply coloured should be selected and placed in the 

 air till partially dry. As the frond dries, little drops of a slimy, bright orange fluid 

 will ooze out from the pores of the receptacle ; and if one of these drops be removed, 

 and placed in a little sea water on the stage of the microscope, it will be found to 

 consist of multitudes of detached antheridia. If these be watched for a short time, 

 the vivacious corpuscles may be seen to issue from them and perform their singular 

 dances. 



The Fucacece are readily known from all other orders of Melanosperms, by 

 having their spores contained in those little spore-cavities, which we have already 

 described. In no other order do such cavities exist. 



The group of plants defined by this character is a very extensive one, comprising, 

 perhaps, one-half of the known Melanosperms. If we view it as also composed of 

 an aggregate of individuals of each species, its relative importance will appear 

 very much greater, for most of the plants of which it consists are social ones, and 

 clothe very large portions of the submarine soil. About 230 species are described 

 by Agardh in his last work, while Kiitzing, (who has introduced many species 

 which are not admitted by other writers) enumerates upwards of 300. Of this 

 large number, hoAvever, I am only able to claim 20 as inhabiting the American 

 shores, and six of these are known only on the Pacific coasts. 



The deficiency of Fucacece is a very remarkable feature of the American marine 

 flora, the common fuci of the eastern coasts being only two, {Fucus vesiculosus 

 and nodosus) and these two scarcely growing south of New Jersey. No doubt the 

 long line of sandy shore which extends from New York Bay southward forbids 

 the production of plants whose natural habitat is on tidal rocks and boulders ; 

 but it is remarkable that on the rock-bound coasts of the North Eastern States, 

 there is no trace of the Fucus serratus or F. canalicidatus Avhich are so widely dis- 

 persed on the European side of the Atlantic. We should not consider this absence 

 of common European forms remarkable, if the Fuci found on the American coasts 

 -WQY& peculiar to them. It is because the two species so abundant in America are 

 also common in Europe, that we wonder at the absence, in the western watei's of 

 the Atlantic, of the equally common forms with which they are associated in the 

 eastern. 



