AS AN AGENT IN PLANT DISPERSAL. 337 



whilst still afloat after a period of 14 months in the water ; 

 during the first spring, however, they were kept in a cool place 

 but exposed to the light, and I thus prevented their germination, 

 I scarcely think that this is at all a common event in our river?, 

 as floating seeds have many enemies. Coming to the liberated 

 dicotyledonous seedlings, I may say that as a general rule they 

 float and thrive at the surface, developing the first few leaves, 

 but not attaining a greater length than an inch or two even after 

 months afloat, and never of course growing into a characteristic 

 plant; though if stranded on a mud-bank, as I proved by experi- 

 ment, they very readily strike into it and develop into the full- 

 sized plant. The behaviour of the floating monocotyledonoua 

 seedlings is much the same ; in nearly all cases it is necessary, in 

 order to develop into a plant, that they are stranded on the mud. 

 I am now, however, trespassing beyond my limits. Space only 

 permits me to make the scantiest of references to a matter in 



which probably lies the parting of the ways between land- and 

 water-plants. 



TJp to this point I have said nothing of the influence of ice 

 on river-drift. In the ice that in a severe winter covers the Lea, 

 and forms at the margins of the Thames, seeds and seed-vessels 

 are in certain localities inclosed in numbers. But for many 



* 



reasons it is not an easy matter to find ice inclosing the drift. 

 The indiscriminate examination of ice-blocks is perfectly useless. 

 However, I may say that I found this winter, in the ice at the 

 riverside opposite Hampton, numbers of the fruits of Rumex 

 conglomerate, Lycopus europceus, and Abacs glutinosa ; and in 

 the Lea ice of last year I found the fruits of Bidens sp., Lycopus 

 europceus, Ranunculus repens, &c; and I may here add that in the 

 ice of the ponds of Epping Forest I found the fruits of Scutel- 

 laria galericulata, Lycopus europceus, Galium palustre, Potamo- 

 geton natans, Carex sp., &c. My experiments show that the ice 

 of an English winter does not affect the germinating power of 

 the seeds inclosed in our ponds and rivers. In tact, during 

 the past winter I have had fruits of the above-named plants, 

 together with those of Ranunculus sceleratus, Atriplex patula, 

 Sparganium ramosum, Alisma Plantago, and Potamogeton nutans, 

 inclosed in ice for twenty days, and the germinating power of 

 their seeds does not seem to be at all affected, quite as large a 

 proportion germinating as in the case of seed-vessels not inclosed 

 in ice. In the shallow water of the Lea I found that when the 



