2o8 CORALS 



The branching of the coral is in one phme and is usually 

 trichotomous, two branches arising opposite one another 

 from a joint of the main stem. 



The conceptacles in this genus are in the form of promi- 

 nent swellings at the terminal extremities of some of the 

 branches, and the pore of each ripe conceptacle is at the apex 

 of this swelling. 



Some of the conceptacles, however, are found not at the 

 extremity but at the sides of the joints. 



The genus Corallina seems to be most abundant in the 

 temperate regions, being very common on the coasts of 

 Great Britain, France, and North America. It occurs in 

 great quantities in some localities in the Mediterranean 

 Sea, where Amphiroa is also found. 



In former times this Coralline was collected, dried, and 

 sold in the shops for medical purposes, but it was not 

 considered to be so potent as the more expansive red coral. 



The deposit of calcareous salts in the tissues of marine 

 Algae is not confined to the genera of the family Corallinaceae, 

 although it is in that family alone that we find the hard 

 massive growths that form a conspicuous feature of the 

 coral constituents of a coral reef. 



It would take us far beyond the limits assigned to this 

 chapter if any attempt were made to describe and classify all 

 the calcareous Algae, but a short statement may be made 

 concerning one of the calcareous Red Algae which is extremely 

 abundant on some coral reefs and may serve as an example 

 of quite a different type of structure. 



Family Chaetangiaceae. — The genus Galaxaura^ (Fig. 

 107) occurs in the Mediterranean and in the warmer seas of 

 the Indian, Pacific, and Atlantic Oceans, and it forms dense 

 clusters of profusely branching thalli attached to rocks and 

 corals by tuft -like roots of branching filaments. The 

 branches are usually cylindrical in form, and they are either 

 not segmented at all or, if segmented, the segments or joints 

 are not so pronounced or so regular as in Amphiroa or 

 CoraUina. The method of ramification, too, is quite different 



' See F. R. Kjellnian, Kongl. SvcHska Vet. Handl. xxxiii. 1900. 



