APPENDIX 543 



of Scotland. (I am indebted to Mr. Millett for his extremely kind 

 assistance in experimenting on this plant about ten years since.) 



Erynghun maritimum. The fruits float in sea-water, as a rule, only 

 3 or 4 days and all sink within a week. After drying for three months, 

 the floating period is only increased by a day or two. Though not at all 

 suited for transport for any distance by the currents, the carpels, on 

 account of their long prickly calyx teeth, would readily become entangled 

 in a bird's plumage, and doubtless they are dispersed usually in that 

 fashion. 



Euphorbia paralias. The seeds float a long time unharmed in the sea. 

 In my experiments at least 90 per cent, remained afloat after six weeks in 

 sea-water. On account of their small size they are liable to be overlooked 

 in beach drift ; but they are to be found stranded on the sands of our 

 .southern coasts, and they came under my notice in abundance in the 

 seed-drift of the Sicilian beaches. 



Glaucmni luteum. — The seeds have no proper buoyancy even after 

 prolonged drying. On account of their oiliness they will float at first on 

 still water ; but they can be made to sink at once or in a day by dropping 

 water upon them. The mode of dispersal is problematical. 



Lathyrus maritimus.- — The seeds are evidently able to float a long time. 

 They were, according to Sernander (p. 178), found in quantities by J. 

 Schmidt cast up on some sand-islets near Falster in Denmark ; and the 

 plant is regarded by Norman as distributed over the coasts of Arctic 

 Norway through the agency of the currents. They have, as observed by 

 Schmidt, considerable floating powers. Some small leguminous seeds, 

 seemingly of this species, which I found in the beach drift of Woolla- 

 combe Sands, Devonshire, floated uninjured for many weeks in sea-water. 



Matricaria maritima, maritime variety of M. inodora. The fruits 

 floated in my experiments unharmed after eight months in sea-water. 

 In an experiment made some years since on the fruits of the inland 

 form I noted that they had little or no buoyancy ; but it is necessary to 

 repeat the observation. Sernander (p. 181) supports Norman's view that 

 these plants are spread by the currents in Arctic Norway. The fruits occur 

 in the Baltic sea-drift and also in fresh-water drift. M. inodora is found on 

 sandy beaches in Nova Zembla. I am inclined to regard the maritime 

 form from the dispersal standpoint as a distinct species. 



Polygonum maritimum. — I have made observations on this plant in 

 Devonshire, the Lipari Islands, and the coast of Chile. As in the case of 

 several other species of Polygonum tested by me the fruits have little or no 

 buoyancy, but inclosed in the perianth they float three or four days. The 

 entire plant floats ; but portions placed in sea-water sank within five or six 

 days. Shore-birds can alone explain the wide distribution of this species. 



The structural characters of some of these fruits or seeds are in their 

 relation to buoyancy discussed on page 115. It may be here observed that 

 the valuable results obtained by Prof. Martins in testing the germinating 



