340 ME. H. B. GIJPPY ON THE THAMES 



in fresh water, sink in a week or two iu sea- water. Those nuts 

 that sank in sea-water usually germinated. In fact, I could get 

 no other nuts to do so, the reason being that the decay of the 

 outer covering of the nut is a necessary step to germination, 

 because upon it depends the opening out of the valvular portion 

 of the endocarp : a sound-looking nut does not germinate ; and 

 thus sea-water accomplishes in a week or two what may take 

 months in fresh water to be brought about. 



A word with regard to the germinating fruits that may reach 

 the sea. Those of Rumex have their germination arrested, and 

 lose by rotting the protruding portion of the radicle ; but, strange 

 to say, should they get into a freshwater estuary after a week or 

 two at sea, the floating fruits will proceed with the germinating 

 process, and an undersized seedling will be prematurely dis- 

 charged, which soon recovers itself and develops the plumule. 

 On the other hand, if a germinating seed of Iris Pseudacorus 

 reaches the sea, the protruding portion of its radicle soon rots 

 off, and the germination is not continued when the seed is placed 

 again in fresh water. There are rare cases, however, where the 

 germinating seed or seed-vessel is not much affected by sea-water, 

 in which, in fact, the carpels of Ranunculus sceleratus germinate. 



Floating seedlings are doubtless carried down to the sea 

 in numbers every spring. Some, such as those of Bidens sp., 

 Nuphar luteum, Mentha aquatica, and Alisma Plant ago, are killed 

 in a day or two and sink to the bottom. Others, like those of 

 Ranunculus sceleratus, Galium palustre, and Rumex conglomeratus, 

 may in some cases float a week or ten days and yet recover. 

 But the recovery is very tedious. A large part of the axis rots 

 off, and the cotyledons often die as well : yet from the mutilated 

 remainder I have raised plants. Still there must be littoral 

 plants that largely owe their distribution to the ability of their 

 seedlings to float and live in the sea. The seeds of Salicornia 

 herbacea, for instance, sink in sea-water even after a winter s 

 drying. Yet they germinate freely in sea-water, and the liberated 

 seedling rises to the surface and thrives. The same, however, 

 cannot be said for the seedlings of Spergularia rubra and Are- 

 naria peploides, plants which frequent, however, sandy shores, 

 whilst Salicornia herbacea is found on muddy flats washed by the 

 tide. I have touched incidentally on these plants, though the 

 subject is foreign to this paper. 



Having dealt very briefly, and cf necessity very incompletely, 



