The South Australian Naturalist. 75 



theory had, in fact, become orthodox scientific opinion, and any 

 heretic who dared to question it in any way was held in dis- 

 favour. The lecturer in a most delightful manner followed the 

 subsequent course of the discussion through Sir John Murray 

 (Avhose theory he characterized as being now "as dead as 

 mutton"), and the other theories put i'orvvard on this question. 

 It was pointed oat that the most difficult feature of Darwin's 

 fine theory was that it demanded everywhere over the wide 

 areas of the tropical oceans a sinking ocean floor. This grave 

 difficulty had been ingeniously met by the engrossing theory 

 of Reginald A. Daly that the remelting of the ice stored up 

 during the last glacial period had raised the level of the oceans 

 of the world the required number of fathoms. The author 

 proceeded to deal with Professor W. M. Davis, the American 

 physiographer, who upheld Darwin, but whose basis of discus- 

 sion was found fault with by the lecturer. Professor Wood- 

 Jones' intimate knowledge of the Cocos-Keeling coral group 

 was made the basis for a comprehensive theory of the forma- 

 tion of fringing reefs, barrier reefs, drowned atolls, and 

 ordinary atolls, starting with a basis of volcanic or other islet. 

 This was conceived as being worn down by wave action to the 

 point where the surface movement of water was no longer felt. 

 U])on this basis the coral polyps built their barrier, rising until 

 the surface of the water was reached. The further control of 

 il:e shape of the reef was held by the lecturer to be w^holly in 

 the hands of the prevailing winds. By a series of diagrams 

 the characteristic atoll shapes were shown as they slowly 

 developed under the influence of the wind. 



Excursion, July 23, 1921. — A large party visited the Botanic 

 Gardens, and were received and conducted by the Director. Mr. 

 F. Bailey. The afternoon was spent wanderino; througli the 

 pleasant paths of that delightful resort, stopping- at points 

 selected by the Director, where plants of new or special interest 

 were to be seen. The various hot-houses, the palm house, the 

 conservatories, and the Simpson fern house Avere also visited, 

 providing a feast of interest for the botanist in a variety of 

 species gathered from all parts of the v\Tjrld. It is notable that 

 many introduced plants grow to greater size and perfection in 

 these gardens than in their native habitat : this is so. for in- 

 stance, of two plants as far apart in size and origin as the 

 Bunya Bunya pine, of Queensland, and the Irish strawberry 

 (arbutus) of Killarney. 



