xxxiii SEED-DISPERSAL AND GEOLOGICAL TIME 513 



that in a short time they thoroughly digested the seeds. Those 

 famiHar with the seeds of our British species of Nuphar and 

 Nymphaea will not be surprised at such a result ; but, unfortunately, 

 the inference drawn from this experiment has been by some 

 extended to aquatic plants in general. Since the seeds or seed- 

 vessels of some aquatic or semi-aquatic plants of the genera 

 Potamogeton, Sparganium, &c., appeared to me to be quite fitted 

 for conveyance without injury in a duck's body, I made several 

 years ago a number of observations on this subject, the results of 

 which were published in Science Gossip for September, 1894. 



Out of 1 3 wild ducks obtained in the London market and stated 

 to have been sent from Norfolk and Holland, eleven contained in 

 their stomach and intestines 828 seeds, which I thus classed : — 



295 seeds of Sparganium in 8 birds 

 41 „ „ Potamogeton „ 3 „ 

 270 „ „ Cyperaceae „ 5 „ 

 222 not identified 



In the case of four birds the germinating capacity of the seeds 

 was tested, and in three cases very successfully. The seeds of 

 Potamogeton, Sparganium, and of the Cyperaceas germinated 

 readily in water, but few of them failing, the process beginning in a 

 few days or a few weeks. At that time I was conducting an 

 extended series of observations on the postponement of germina- 

 tion of the seeds of aquatic plants, the results of which were pub- 

 lished in the Proceedings of the Royal Physical Society of Edinburgh 

 for 1897. It was there shown that the seeds of these plants often 

 postpone their germination to the second and even to the third 

 spring. It thus happened that, whilst seeds obtained from the 

 stomach and intestines of the wild duck germinated in a few days 

 or weeks, I had to wait often a year and more for such a result 

 with seeds in their ordinary condition. This was well brought out 

 in another experiment made on a domestic duck, which I have 

 described on page 369. That wild ducks are to be regarded in the 

 light of " flying germinators " is thus very evident. 



Summary. 



(i) In explanation of the shifting of the source of the Polynesian 



plants from the New to the Old World, it is suggested that during 



the glaciation of the northern hemisphere the Indo-Malayan plants 



entering this region were "cornered" in the tropical Western 



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