00 Proceedings of tHeI 



less tliiiii tweiily. Vi'f,felativo ])if)])!ii,'ation is (^llVc-led hv llie 

 rliizoiiies. I'lijils wliirli 1 raised in llMfi Irniii float ii)<^' scedlinj^s, 

 tilt! ofls])riii<,' of seeds liarvested in I'.H"), flowered for the first 

 time in June 11)19, at the foninieneenient of their fourth year. 



Tiie seeds numher from forty or I(\ss, to sixty or more, per 

 capsule, and there are sometimes as niaiiy as nine good capsules 

 on a spat he. IJel'ore maturity tlie seeds are white and saturated 

 tliron<j;hout with moisture; the capsule hegins to dehisce before 

 tilt! entl of September; a?ul then the dry brown testa of th(> ripe 

 seed is glazed externally, but not internally, and the K'ernel, which 

 consists of the inner integument, the horny entlosperm, and the 

 straight embryo, lies loose within it. 



The seeds are carried long distances overland by diving birds, 

 which are the most im|)ortant of all the dispersal agents, and I 

 think it quite ])robabIe that the altitudinal range in this country 

 is dependent to some extent upon that of the birds that disperse 

 the seeds. The floating seedlings get entangled in tlu! legs of 

 domestic duc!\S, and are almost certainly dispersed in this way by 

 our native swinnning birds. The Avind is the least im])ortant 

 of the dispersal agents. Wlie)) the ground around ])ermits, it 

 extends the area of an existing colony outward, but disjjersal by 

 the wind alone is practically confined to its l)lowing the flat seeds 

 a few yards away from the jiarent plant. In conjuiiction with 

 dead leaves, however, it is responsible for a good tleal of wider, 

 but still local dispersal, and in conjunction with water it blows 

 the floating seeds from one end of a lake or pond to the other. 

 Seeds which have been ice-borne germinate freely, and bits of 

 floating rhizome help to disperse the species since, when stranded 

 on freshwater mud, they reproduce the plants vegetatively. The 

 flat seeds are adapted to dispersal (1) on the backs of diving birds, 

 to w hich they adhere as the diver rises from below to the surface 

 upon which they are afloat, and (2) by being blown short distances 

 by the wind. In the flrst event they are useful for founding 

 fresh colonies, often at a great distance, and in the second for 

 extentling the area of one alreatly existing. The round seeds, 

 numerically only about one to four of the flat, serve to All up the 

 death gaps at home and along the margins of running waters. 



Sunk seeds possess, while floaters are without, an internal 

 supply of water between the testa and the kernel, which causes 

 them to sink. They yield slightly higher percentages of germina- 

 tion than the floaters. In experimenting, however, one has to 

 make tjuite sure that the seeds have sunk for this reason, and not 

 merely because of the weight of their superincumbent accretions. 

 Intermittent drought reduces the percentage, and dessiccation 

 during the autumn and winter inhibits it almost completely for 

 the first season, except when damage to the testa has let in 

 water to soften the hardened and shrunken endos])erm before it 

 is too late. 



Dealing for the moment only with first-year seetis — tbos(> that 

 are less than a year old — those which are on or at the bottom of 

 shallow water and those which are in, not on, saturated mud, 



