370 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1962 



within the female plant. There it grows into a small mass of cells 

 and produces a special group of spores inside the old female concep- 

 tacle. Each of the spores must now be released in its turn — through 

 the same pore by which the male cell entered — into the sea water out- 

 side. There it finds a rocky surface yet unoccupied, upon which to 

 spread the first cells of a new, non-sexual generation. 



Calcareous members of the red algal family Corallinaceae are the 

 most prevalent of the stone plants, so widely distributed that they 

 form part of the marine flora of every maritime nation of the world. 

 In the glacial fiords of Norway or Greenland one finds thriving beds 

 of nullipores. Crustose corallines cover wave-beaten rocks from Kam- 

 chatka to Chile, and from Newfoundland to Kerguelen. Delicate, 

 flakelike forms live on the leaves of turtlegrass in Cuba, and on eelgrass 

 in Japan. The jointed bossiellas dwell no less successfully in the cold, 

 clean tide pools of Vancouver Island than beside sewer outfalls in 

 southern California. The dainty janias are equally prominent in 

 spongy, algal turfs on the reef flats of East Africa and in those of 

 Micronesia. Despite the ubiquity of these plants, they have been little 

 studied and remain among the least-known organisms of the sea. 



Since plant scientists have generally neglected the calcareous algae, 

 their importance in many natural phenomena has been little recog- 

 nized. This is particularly true of one of the most extraordinary of 

 all marine geological phenomena — the tropical "coral" atoll. The 

 story of the calcareous algae's contribution to the formation and 

 growth of the atoll is so remarkable and so little known that it seems 

 particularly appropriate to tell something of it here. 



During the last century, a number of naturalists made visits to the 

 coral reefs of the Indo-Pacific region and, from their observations, 

 theories of atoll origin and growth were developed (Natural History, 

 March and April 1959). Charles Darwin, James D, Dana, Sir John 

 Murray, Alexander Agassiz, Reginald A. Daly, and others inter- 

 preted the atoll from a geological or zoological standpoint. But each 

 investigator failed in every instance fully to recognize the importance 

 of calcareous algae as controllers of reef development. It was not 

 until Sir Edgeworth David's South Pacific expedition (1896-1898) 

 that evidence was obtained to establish the significance of plants in 

 this relationship. Since then only an occasional marine botanist has 

 written on the subject and expanded the knowledge of the role algae 

 play in atoll formation. As a result, some long-standing and wide- 

 spread misconceptions are still prevalent. 



Some of the pertinent facts are : First, nullipores have been found 

 to be among the principal components of atoll reefs in a great majority 

 of cases. In some instances, they are almost the only visible com- 

 ponents, to the virtual exclusion of coral animals. 



