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bladders off shore in six fathoms of 

 water. Indeed, each variety seems to 

 show a preference for certain conditions 

 of submergence, aeration, wave impact 

 and illumination to which it is particu- 

 larly adapted, and when these condi- 

 tions approach the optimum one will find 

 the species in greatest abundance and 

 perfection. 



Unlike the related rockweeds, kelps 

 are not known to reproduce by means 

 of sperms and eggs. The sole repro- 

 ductive bodies which they form are 

 asexual spores or gonidia, produced 

 sometimes in large numbers, a hundred 

 or more at a time, in microscopic sacs. 

 These sacs, intermingled with sterile 

 filaments, are aggregated upon special 

 surfaces of the laminae in patches of 

 more or less regular shape and size. 

 Such patches are known as sori. Some- 

 times they occur upon the ordinary 



