338 ME. H. B. GUPPf ON THE THAMES 



* 



ice was frozen to the bottom, the underlying mud was also frozen 

 for an inch or so and came up in one continuous mass with the 

 ice. In this manner I lifted up in the ice-slabs shoots of Myosotis 

 palustris, which I have still alive. However, as there is no space 

 in this paper for dealing with the subject of ice-transportal, I 

 can only here remark that seeds of JSuphar luteum and Nymphcea 

 alba 9 drupes of Sparganium ramosum, together with nuts of more 

 than one species of Potamogeton, which were 12 days in frozen 

 mud in my saucers, freely germinated. 



Though ice does not affect the ultimate germination of the 

 seeds and seed-vessels inclosed in it, it sends great numbers ot 

 them to the bottom after the thaw. The nuts of Potamogeton 

 natans sink in quantities. Quite half of the fruits of Sparganium 

 ramosum go to the bottom. Two-thirds of the carpels of Ranun- 

 culus repens, about half of the fruits of Atriplex patula, and 

 many of the carpels of Alisma Plant ago also sank. On the 

 other hand, the seeds of Iris Pseudacorus and the fruits of Ramex 

 conglomerates, Lycopus europceus, and Scutellaria galericulata 

 did not sutler much. The seeds and seed-vessels that sank 

 after being inclosed in ice germinated freely afterwards, and 

 in some cases the sinking evidently assisted germination. The 

 cause of the sinking is to be found in the ice affecting the 

 vitality of the outer coverings or buoyant portions of the fruit ; 

 a process which in the ease of the fruits of Sparganium ramosum 

 and Potamogeton natans directly aids germination. Another 

 effect of ice is to send half the fronds of floating Lemnce to the 

 bottom, the rest surviving to the spring. It may, in fact, be 

 generally stated that after a thaw the surface of a river is cleared 

 of a large proportion of the floating drift. . . . When a germi- 

 nating seed or seed-vessel is inclosed in ice, germination is 

 arrested ; but after the thaw, in the case of Rumex conglomerates, 

 for instance, the process is often rapidly completed and a dimi- 

 nutive seedling is prematurely discharged, which soon shows the 

 first leaf and evinces other signs of vitality. If, however, germi- 

 nating carpels of the two species of Ranunculus repens and 

 aquatilis are inclosed in ice, many of them do not complete the 

 process after the thaw, and rarely does a healthy seedling survive. 

 The germinating carpels of Ranunculus sceleratus fare somewhat 

 better. Should the seedlings of the plants above named be in- 

 closed in ice, many of them will produce the plumule after a 

 continuous period of 8 or 10 days in ice. In fact, some seedlings 



