1850.] Linnean Society. 79 



dotted leaves, the real fructification of the genus bearing no resem- 

 blance to that of Ferns, though to persons slightly acquainted with 

 the subject the arranged dots on the leaves might readily suggest 

 the comparison. 



" With regard to the non-existence of roots in the Gulf-w^eed as 

 a proof of specific distinction, it is to be observed that the genus 

 Sargassum, now consisting of about sixty species, is one of the most 

 natural and most readily distinguished of the family Fucacea, and 

 that there is no reason to believe that any other species of the genus, 

 even those most nearly related to, and some of which have been 

 confounded with it, are originally destitute of roots ; though some 

 of them are not unfrequently found both in the fixed and in con- 

 siderable masses in the floating state, retaining vitality and probably 

 propagating themselves in the same manner (see Forskal, Fl. ^gypt.- 

 Arab. p. 192, n. 52). It is true indeed that a Sargassum, in every 

 other respect resembling Gulf- weed, has, I believe, not yet been found 

 furnished either with roots or fructification, neither Sloane's nor 

 Browne's evidence on this subject being satisfactory*. But the 

 shores of the Gulf of Florida have not yet been sufficiently examined 

 to enable us absolutely to decide that that is not the original source 

 of the plant ; and the differences between the Gulf- weed and some 

 other Sargassa, especially <S. nutans, are not such as to prove these 

 two species to be permanently distinct. The most remarkable of 

 these differences consists in the leaves of the Gulf- weed being uni- 

 formly destitute of those dots or areolae so common in the genus 

 Sa?-gassmn, and which are constantly present in S. nutans. These 

 dots, in their greatest degree of development, bear a striking resem- 

 blance to the perforations or apertures of the imbedded fructification 

 in the genus. But as the receptacles of the fructification, as well as 

 the vesicles, are manifestly metamorphosed leaves ; and as the pro- 

 duction of fructification is not adapted to the circumstances in which 

 the Gulf-weed is placed, it is not wholly imj^robable, though this 

 must be regarded as mere hypothesis, that the propagation by lateral 

 branches, continued for ages, may be attended with the entire sup- 

 pression of these dots. 



" That the Gulf-weed of the great band is propagated solely by 



* See Sloane's Jam. i. p. 59. I have examined Sloane's specimens in 

 his Herbarium ; they belong to Gulf-weed in its ordinary form, and are alike 

 destitute of root and fructification ; hence they are probably those gathered 

 by him in the Atlantic, and not those which he says grew on the rocks 

 on the shores of Jamaica. Browne's assertion to the same effect is probably 

 merely adopted from Sloane. 



