Praegkr — The Buoi/anc;/ nf the Seeds of some Britannic Plants. 59 



buoyaucy of the seeds giveu in my list, oue might perhaps divide my figures 

 by three. But while this variability exists among the individual seeds, it was 

 found that if any batch of seed be divided, its sections behave very uniformly 

 as regards maximum and minimum buoyancy, showing that the test 

 employed is a satisfactory one. 



At the same time, batches of seed collected in different places at different 

 times occasionally displayed, when compared, a difference in their buoyancy 

 far exceeding the difference observed within any one batch. While some of 

 the discrepancies between Gruppy's results and my own, as shown in the table, 

 are possibly explicable by different conditions of experiment, the same cannot 

 apply to different batches tested by myself under similar conditions. 



The most striking cases of variability of buoyancy, taken from the tablo, 

 are listed below : — 



Ranunculus sceleratus — SJdays. (Guppy, 6-12 months.) 



R. repens — 3J days. (Guppy, 6-12 months.) 



Radicula palustris—S houvs, 12 dajs. 



Raphanus Raphanistrum (dry fruit) — 5 days, 4 months. 



Comarum palustre — 2 months, 15+ months. (Guppy, 12+ mouths.) 



Raloscias scoUcum — 5^ days, 2J months. 



Bidens cerniia — 3 weeks. (Guppy, 6-12 months.) 



Helminthia echioides — 12 hours, 1 day, 15+ months. (Guppy, 0-7 days.) 



RJiinanthus Crista-Qalli — 2 weeks. (Guppy, 6+ months.) 



Lycopus eiiropaeus — 2\ days, 15+ months. (Guppy, 12+ months.) 



Mentha imhescens — 6J days. (Guppy, 6+ months.) 



Atriplex patula — sinks at once. (Guppy, 6+ months.) 



Euphorlia Paralias — 4 days. (Guppy, 1-6 months.) 



Potamogeton polygonifolius — IJ day. (Guppy, 6-12 months.) 



Sagittaria sagittifolia — 1 week. (Guppy, 6+ months.) 



Iris Pseud-acorus — 85 weeks. (Guppy, 12+ months.) 



Sparganiiim erectum — 1 week, 15+ months. (Guppy, 12+ months.) 



Epipactis longifolia — 1 month, 15+ months. 



Blysmus rwfus — 1 week. (Guppy, 1-6 months.) 



Carex paniculata — 4 weeks. (Guppy, 12+ months.) 



C. elata — 2 months, 9 months. 



C. panicea — 2 days, 15+ months. 



C. paradoxa — 3 days, 15+ months. 



C, vesicaria — 10 days, 42 days. 



