62 



are pierced at the base, the water escapes during low tide, and 

 air is liable to take its place. On the return of the tide all the 

 air is not expelled, but a certain amount remains as a bubble, 

 which causes the frond to become bouyant. Many plants, owing 

 to the presence of this imprisoned air, break away from their 

 moorings, and frequently bring with them a piece of other sea- 

 weed or a minute fragment of rock. In Brittany Colpomenia 

 has caused the loss of young oysters, owing to its rising to the 

 surface in this way. The plants occur in great quantity on the 

 oyster-beds, and when the fronds become buoyant and break 

 away, they are apt to detach with them some of the spat or young 

 oysters. 



Habitat. 



Colpomenia occurs on rocky shores, where there is shelter 

 from rough water. It is found in autumn, winter and spring, 

 but is most abundant in April and May. After June it practically 

 disappears. It frequents pools and rocks near low-water mark. 

 At Swanage it is found on the rocks below the Grosvenor Hotel, 

 and at Weymouth in the pools south and west of the Nothe Fort. 

 At Studland it is abundant on the rocks leading to the "Old Harry 

 Rocks, but in all cases search must be made at low tide. 



Further Information Required. 



Further observations are needed on the distribution of Col- 

 pomenia in Britain. Its luxuriance and rapid spread in Devon 

 and Dorset lead one to expect that it will invade Hampshire and 

 Sussex, but so far no one has recorded it from these counties. 

 Notes on this point are important in connection with 

 the possibility of its spreading through the Straits of 

 Dover and finding a suitable habitat on the oyster beds 

 of Kent and Essex. Being a southern plant, it is 

 possible that the water of the North Sea may be too cold for its 

 requirements, but as some of the largest specimens on record 

 have been found at Studland, it is evidently quite at home in the 

 waters of the Channel. Though abundant in the Scilly Isles, :.o 

 records exist from N. Cornwall or N. Devon. 



The Island of Jersey from a Natural Science 

 Point of View. 



By Dr. G. E. J. Crallan, M.A. 

 (Delivered as a General Lecture at Trinity Hall, April 13th, 1912.) 



YK7HILE spending the past winter in Jersey it occurred to me 

 that some account of the Island, with illustrations, might be 

 of sufficient interest to form the subject of a lecture before our 

 Society. This Island is a perfect little Kosmos in itself, but the 

 time at my disposal will not allow me to give an account of the 



