342 MR. H. B. GUPPT ON THE THAMES 



Scirpus nuts from two wild ducks purchased in the latter part 

 of February have since germinated. 



Next I take the instance of Ceratopftyllum demersum. The 

 plant flowers freely in the Lea ; but I never found a mature 

 nut, and in fact, after much disappointment in my greenhouse, 

 I brought only a solitary fruit to maturity. The fruit sinks 

 like a stone, and the plant is soon killed in sea-water ; so that 

 we cannot look to water for the dispersal of a plant that has 

 established itself nearly all over the globe. Rein found it in 

 the Bermudas, and Home in the Fijis; and Hemsley classes 

 its nuts with thdse seed-vessels that are probably transported 

 by birds. For similar reasons, the widely spread Polygonum am- 

 phibium must owe its dispersal to birds ; its young stems or 

 shoots,! -1£ inches long, are to be found floating in the Thames and 

 the Lea in January and February ; but its nuts will only be found 



in the mud. 



Myos 



palustris cannot float very long even after drying ; and for their 

 dispersal we can look only to the transporting power of ice 

 bearing frozen mud underneath it, or to the agency of birds. I 

 shouldadd that one of the most conspicuous features of the drift 

 of the Thames and the Lea, both in the winter and in the spring, 

 are the floating shoots of Myosotis palustris ; they will float only 

 two or three days in sea-water and are unable to survive. 



With regard to the two Water-Lilies, I cannot help thinking 

 that they owe their dispersal to birds. When the fruits of 

 Nymplicea alba rupture, the seeds, buoyed up by tiny bubbles of 

 air confined in their gelatinous arils, can float a day or two, but 

 that is all. The aril decomposes, the bubbles escape, and the 

 seed sinks. Id a different fashion, when the fruits of Nuphar 

 luteum open, the white carpels, with their numerous seeds, float 

 away down the stream, and may remain at the surface a few 

 days, when they decompose, sink, and cairy the seeds to the 

 bottom. The process of detachment of the carpels may be 



watched in the river Eoding : as they float down the stream, 



they are conspicuous on account of their whiteness, and might 

 easily attract birds. Water-fowl have been observed pecking 

 the Nuphar fruits that abound on the surface of the Wanstead 

 lakes ; and I have noticed one or two of the fruits in these lakes 

 half eaten, as if by birds. The fruits of Nymphcea alba being 

 submerged do not present the same opportunities to birds ; 

 but when one bursts, a process sometimes accomplished in a iew 



