Feb., 1909,] The Sporophylls of Lessoniopsis. 439 



into main branches, floats and photosynthetic areas as in Egre- 

 gia, was accomplished by steriUzation and modification of poten- 

 tial sporophylls. At first thought it might be supposed that 

 Lessoniopsis, by the possession of the characters of both lines, 

 should be regarded as representing a basal point from which 

 both subfamilies had originated by following divergent lines of 

 evolution. Such seems, however, an untenable view. There 

 are none of the indications of a primitive character for Lessoniop- 

 sis. It is, in the judgment of the writer, clearly a member of 

 the Lessoniatae. The characteristic branching of that series 

 is the doininant character of Lessoniopsis and gives it the form 

 and structure of its adult body, while the proliferated sporophvlls 

 do not make their appearance until the plant has practically 

 completed its development. This is in great contrast to the 

 Alariatae in which the sporophylls appear very early even in the 

 lowest members where their function is almost exclusively repro- 

 ductive and is not called into activity until maturity. 



The unlooked for appearance of such a character among the 

 Lessoniatae is to be considered as a striking example of the 

 remarkable adaptability of the whole family of kelps by virtue of 

 which we find in more than one plant structures belonging to 

 lines otherwise entirely disconnected from it. This makes it 

 difficult to construct a satisfactory classification of the genera 

 because inconsistencies from this cause are almost unavoidable 

 whatever principle of classification is used. The descent of the 

 kelps seems to be a much interwoven fabric which has been sur- 

 prisingly little divided up into narrower strands by the loss of 

 plasticity by which each line is narrowed into its own special 

 channel of evolution. This great variability along with manv 

 other features of the kelps leads to the view that the group is still 

 in its youth and evolving rapidly. 



LITERATURE. 



Griggs, R. F., 1909. Juvenile Kelps and the Recapitulation 

 Theory. Am. Nat. 43: 5-30. 



Reinke, J., 1903. Studien z. Vergl. Entwickelungsgeschichte 

 der Lamimaraiceen. Kiel. 



