228 INTRODUCTION TO CRYPTOGAMIC BOTANY. 



that though they abound iu New Holland and the West 

 Pacific, they are nearly absent from analogous positions in the 

 longitude of South America, though there is nothing to pre- 

 vent the fullest interchange between New Zealand and the 

 temperate seas of South America. 



215. " Throughout all latitudes the two divisions of Fucace^, 

 Fucoidece, and Cystoseirece, form that prevailing marine vege- 

 tation to which the name of sea-weed is commonly applied ; 

 and the different genera so far arrange themselves within 

 geographical limits, as to present, with few exceptions, a most 

 harmonious assemblage. Thus in the opposite cold and frigid 

 zones, the waters are inhabited by certain genera of FiicoidecB, 

 which are in a great measure representatives of one another, 

 as in the north-east zone Fucus proper and Himanthalia are 

 represented in analogous southern zones by D. Urvillcea and 

 Sareophycus. 



"None of these approach the tropics, for the Fucoidece 

 abound towards the poles, and there attain their greatest 

 bulk, diminishing rapidly towards the equator, and ceasing 

 some degrees from the line itself. The representatives of the 

 CystoseirecB, in the higher latitudes of the opposite hemi- 

 sphere, are equally appropriate with those of Fucoidece; for we 

 have in the north cool zone Cystoseirece and Halidrys, repre- 

 sented in the 5outh cool zone by Blossevillea and Scytothalia, 

 while the immense genus Sargassum finds its maximum in 

 lower latitudes, and under the equator itself." Hook. Fl. Ant. 

 Scytothalia is found on the icy shores of the Antarctic in the 

 longitude of Cape Horn, though entirely unknown in warmer 

 seas of the same longitude, and supposed to require a high 

 temperature for its development, and, what is curious, under 

 one of the very finest species of the group to which it belongs. 



216. Fucacece* differ from all other tribes of Melanosperms 

 in having their fructifying organs disposed on the walls of con- 

 ceptacles, the exact analogues of the perithecia of Sphccriacece, 

 as Xylaria, immersed in the fronds, or rather in particular 



* Consult on the fecundation of Fucacece, in addition to other 

 memoirs cited from Annales des Sciences Naturelles, those in ser. 2, 

 vol. 19, p. 266 ; s6r. 4, vol. 2, p. 197. 



