VIl] LITHOTHAMNION. 185 



Agassiz^ has given aa account of the occurrence of immense 

 masses of Nullipores {Udotea, Halimeda etc.) in the Florida 

 reefs; his description is illustrated by good figures of these 

 algae. 



In the Mediterranean there are true NuUipore reefs, which 

 are interesting geologically as well as botanically. Walther^ 

 has described one of these limestone-banks in the Gulf of 

 Naples which occurs about 1 kilometre from the coast and 30 

 metres below the surface of the water. Every dredging, he 

 says, brings up numberless masses of Lithothamnion fasciculatum 

 (Lamarck), and L. crassum (Phil.). Between the branches of the 

 algae, gasteropods and other animals become completely enclosed 

 by the growing plants, while diatoms, foraminifera, and other 

 forms of life are abundant. Water percolating through the 

 mass gradually destroys the structure of the algal thalli, and 

 in places reduces the whole bank to a compact structureless 

 limestone. 



The same author' has also called attention to the importance 

 of Lithophyllum as a constructive element in the coral-reefs oft' 

 the Sinai peninsula. 



Lithothamnion a typical genus of the Corallinaceae may be 

 briefly described. 



Lithothamnion. Fig. 37. 



Philippi"* was the first writer to describe this and other 

 genera as plants. He gave the following definition of Litho- 

 thamnion : 



"Stirps caloarea rigida, e ramis cylindricis vel compressiusoulis 

 dichotoma ramosis constans." 



The thallus of Lithothamnion grows attached to the face of a 

 rock or other foundation, and forms a hard, stony mass, assuming 

 various coralline shapes. The exposed face may have the form 

 of numerous short branches or of an irregular warty surface. 



1 Agassiz (88) vol. i. p. 82. *= Walther (85). 



3 Ibid. (88) p. 478. " Philippi (37) p. 387. 



