438 



The Ohio Naturalist. 



[Vol. IX, No. 4, 



they are usually falcate, widest at the extremity and cuneate 

 at the base. After that length is reached they appear to grow 

 more slowly and to broaden as well as lengthen till they are as 

 long as ordinary laminae and have semicircular or subcordate 

 bases (fig. 3). 



The diverse modes of origin of the two kinds of laminae 

 emphasizes the importance of the dimorphism of the laminae. 

 This was the character which caused Reinke ('03) to separate 

 this plant from Lessonia and erect for it the genus Lessoniopsis. 

 It is apparent that this is as valid a genus as any of the kelps. 



The origin of sporophylls in Lessoniopsis; about one-half natural size 



These proliferated sporophylls give Lessoniopsis a very great 

 interest from a phylogenetic point of view, for in them this plant 

 shows the characters of both of the principal lines of development 

 in the kelps. In the Lessoniatae branching is accomplished 

 exclusively by the perforation of the meristem as in the sterile 

 branches of this genus. In the Alariatae it is brought about 

 altogether by proliferations from the transition region ; these 

 give evidence that they were originally restricted to reproductive 

 functions as in this plant and that their further development 



