A STUDY OF THE GENICULA OF CORALLINE. 7 



type. Vet the genicula of the present type characterise a species in 

 ;i great degree. It would be better, therefore, to mention them on 

 the same level with the other forms (fig. E). 



The above mentioned live types are easily discernible with the 

 naked eye. The divergency of the genicula into these types is due to 

 the difference of the modes in the early stage of their development. 

 Some minute account of the histological views will be given lli the 

 following chapters. 



THE POSITION OF GENICULA. 



The embryonal stage of the Corallinœ is a mere thin calcareous 

 incrustation upon a substratum. In this stage it is not easily 

 distinguished from a sterile form of some Melobesiœ. The tiny 

 epiphytic species, such as Corallina pusilla and Cor. radiata have their 

 basal incrustation in the shape of a verruculose circular disc. 



Every member of the Comllime, however, soon develops a 

 mammilary process perpendicular to the surface of the incrustation. 

 The process becomes provided with an uncalcitied joint, the primary 

 or the basal geniculum, slightly above the level of the surface of the 

 incrustations, cf. Heydrich's paper on " Lithothanmion von Helgo- 

 land." 1 -' The mammilary process continues to grow upward acropetal- 

 ly, .having the geniculum at fixed distances. The intergenicular 

 portions are so-called articuli. 



The intergenicular distance or the height of an articulus is always 

 comparatively short at the basal part of a frond. As the plant grows 

 larger, the successive upper articuli become larger and larger, some- 

 times compressed simultaneously, inclining to its proper shape in 

 each species. This circumstance is nearly similar in every member 

 except tiny and epiphytic forms. 



I). P. 79. 



