592 SCIENCE PROGRESS. 



Guppy (8), after study of the agency of the Thames and 

 Lea in the dispersal of plants, adopts similar views. It is 

 said that, speaking generally, all seeds and fruits in the 

 drift of spring have floated through winter ; this statement 

 is not merely based on their occurrence in the spring-drift, 

 but also on a series of control experiments. Germination 

 may be delayed till the next year, seeds o{ Lris pseudacorus 

 having- germinated afloat after immersion of fourteen 

 months ; growth in spring had been stopped by placing 

 the seeds in a cool place. There are scarcely any seeds 

 and fruits common in the drift of these rivers that will not 

 float for months in sea-water and germinate afterwards. 

 Fruits of Sparganiinn ramosmn germinated after flotation 

 of twelve months in sea-water. Those of several species 

 'survived' immersion of three to five months, their limit of 

 buoyancy not having been then reached. Fruits of three 

 species germinated after immersion of months in sea- water, 

 the density of which had been raised to i "05 by addition 

 of salt; the average density at 0° C is i •02975.^ Some 

 seeds, as those of Lenina minor, only resist flotation of a 

 few days. It is further stated, and this is important with 

 regard to the observations of Salter and White, that 

 sinking of seeds need not involve loss of ' vitality '. 



Ewart (9) mentions that immersion of seeds of peas 

 i^Pisuni sativum ?) for five days in water reduces the per- 

 centage of germinating seeds to 60 per cent. ; this fell to 

 o per cent, after immersion of fourteen days. With Phaseolus 

 v2Llgaris (haricot) the latter percentage is reached after ten 

 days, with Triticum {vidgare ?), Hordeum {disticJittm .^) and 

 Linum usitatissimum, after three weeks, whereas 17 per 

 cent, of seeds of Cannabis sativa germinated after exposure 

 of four weeks. These experiments contravene distinctly 

 those of Guppy ; this is perhaps explicable on the assump- 

 tion that in this case not dormant but germinating seeds 

 were killed: at all events this is supported by the conditions 

 and results of the experiment. 



Horticulturists have long known that steeping seeds in 

 hot water accelerates and augments their power of germina- 

 ^ Treatise on Chemistry, Roscoe and Schorlemmer, i., 266. 



