Miscellaneous . 317 



algologists, or several as described by some autliors, there are in 

 reality two distinct species, commonly known under the name of La- 

 minaria dUjitata. 



In the tissues of one of these plants, the symplocenchyma pre- 

 dominates, in the other the merenchyma ; the stalk of the former 

 also presents concentric rings and mucifevous canals, of which the 

 other is completely destitute. The muciferous canals which are 

 wanting in the stems of many Laminarioi exist in their fronds, and 

 the author considers that these organs exist normally in the tribe of 

 Laniinai'iacece, and arc more or less developed in all parts of those 

 plants which are covered with mucilage. 



The vegetation of the two species is very different, and the details 

 which have been given as to the singular manner in which Laminaria 

 digitata renews its fronds, only applies to one species. In the first 

 species the stem is perennial, and regularly increases in length and 

 thickness every year, forming a new concentric layer at its base, 

 exterior to the old ones, and corresponding with a new whorl of roots 

 which are developed above the others ; at the same time a new 

 lamina is formed at the base of the old frond, which being separated 

 from the new frond by a very narrow constriction, at last falls off 

 altogether. These phseuomena furnish a means of ascertaining the 

 age of the plant, each concentric layer at the base of the stem, or 

 each row of rootlets, corresponding with the annual production of a 

 new frond. The second species appears to have no such determinate 

 periods of vegetation ; the frond grows in a continuous and uniform 

 manner, the stem presents no concentric layers or superposed whorls 

 of rootlets, and no exact indications of age can be derived from the 

 length or the thickness of the stem. 



As all observers, with the exception of Clouston, have confounded 

 the two species under the Linneean name, the author considers that 

 it would only serve to continue the confusion if this name be applied 

 to either of them ; he therefore proposes to retain Edmondstone's 

 name, L. Cloustoni, for one species, and to give the other the name 

 of L. flexicaulis. He gives the following diagnoses of the two 

 species : — 



1. Laminaria Clousfoni. L. fibris radicalibus verticillatim ra- 

 diatimque dispositis, stii)ite erecto rigido cylindrico rugoso, ad basin 

 valde incrassato, versus apicem sensim attenuato, in laminam multi- 

 fidam abrupte expanso. 



2. Laminaria jlexicauUs. L. fibris radicalibus ineequaliter dis- 

 positis, stipite flexili Isevi tereti vel subcompresso, interdum basi 

 subconstricto subfusiformi, sursum complanato, in laminam inte- 

 gram vel multifidam sensim abeunte. 



In his observations on the genus Laminaria, the author remarks 

 that the Algse forming the genus Ilea of Areschoug must be ex- 

 cluded from Laminaria, as they differ from it in structiu'e and fruc- 

 tification. L. brevipes, Ag. and L. derrnatodea, Lapyl. also differ in 

 several respects, especially in the form of the root ; he places them 

 provisionally in the genus Haligenia. The genus Hafgygia, formed 



