206 



CORALS 



There are two more coral Algae belonging to the family 

 Corallinaceae to which some reference must be made, 

 although neither of them play the same important part in 

 the construction of reefs and sea-bottoms as the corals that 

 have just been described. 



They belong to the Group B (see p. 200) of coral plants 

 which show a discontinuous deposit of calcareous matter 

 so that both stem and branches consist of a series of cal- 

 careous joints linked together 

 by non-calcareous internodes. 

 This is the same " admirable 

 contrivance of Nature " that 

 has previously been described 

 in the Alcyonarian genus Isis 

 to protect the plants from the 

 violent motions of the sea 

 (see p. 121). 



Amphiroa. — The first of 

 these is Amphiroa (Fig. 106), 

 a genus having a wide dis- 

 tribution in tidal and shallow 

 waters of tropical and sub- 

 tropical seas. In many locali- 

 ties, such as on the southern 

 coast of California, a species 

 of Amphiroa [A. calif ornica) 

 occurs in enormous quantities 

 in sea pools at low water, and 

 masses of it are thrown up on the beach by the waves. 

 The miniature forests of this bright purple - red coral 

 which cover the rocks in the shallow pools and form a 

 shelter for a great variety of little fish, Crustacea, and other 

 interesting kinds of animal life, are in the bright sunshine 

 the scene of a wonderful display of brilliant colours equal 

 only to what may be seen on a greater scale on the coral 

 reefs. 



Although Amphiroa exhibits considerable variation in 

 size and in manner of growth, the plants are rarely more 

 than five or six inches in height, the joints being 3-6 mm. 



I'"iG. 106. — Amphiruii califoniica. 

 Nat. size. The fragment on the left 

 X 2 shows the swollen conceptacles 

 at the ends of the branches. 



