132 



ELIZABETH W. DAVIES 



is indicated between these species with similar and consecutive chromosome numbers; 

 for the pollen of hybrid plants is never completely sterile, and fertility usually ranges 

 from 20 to 35 per cent (Table 2). 



The hybrids detected in the field between British members of this aggregate will 

 now be briefly discussed. 



Table 2 



Natural hybrids in the C. flava aggregate 









% Pollen 











fertility 



Localities 



1. C. flava 



X 



C. lepidocarpa 



29% 



Lake Carezza, Dolomites, N. Italy. 



2. C. flava 



X 



C. demissa 



22% 



Ti J W 7 J T T .1 • . T 



Koudsea Wood, liaverthwaite. Lanes. 



3a. C. lepidocarpa 



X 



C. demissa 



22% 



Teesdale, Durham. 



subsp. lepidocarpa 













X 





24% 



Derby Fen, Norfolk. 





X 



,, 



30% 



S. Cerney, Glos. 





X 





3d% 



TLJ"! _i CI » C J 



rlokatorp, bkane, bweden. 





X 





25% 



Krogenbund Mose, Zealand, Denmark 



b. C. lepidocarpa 



X 



C. demissa 



32%, 



Loch Tummel, Perth. 



subsp. scotica 













X 





35% 



Creag-na-Caillich, Perth. 





X 





33% 



Creag-an-Lochan, Perth. 





X 





35% 



r)en-y- Vrackie, ritlochry, Perth. 





X 



>> 



28% 



Ben Dorain, Argyll. 





X 



> t 



30% 



Glen Doll, Clova, Angus. 





X 





31% 



Cwm Glas, Snowdon, Caernarvon. 



4. C. lepidocarpa 



X 



C. serotina 



25% 



Wicken fen, Cambs. 





X 





20% 



S. Cerney, Glos. 



5a. C. demissa 



X 



C. serotina 



29% 



S. Cerney, Glos. 



h. C. demissa 



X 



C. serotina var. cyperoides 



26% 



Shapwick, Somerset. 



6a. C hostiana 



X 



C. lepidocarpa 



subsp. lepidocarpa 



0% 



Chippenham Fen, Cambs. 



b. 



X 



C. lepidocarpa 

 subsp. scotica 



0% 



Loch Tummel, Perth. 





X 



n 



0% 



Waulk Mill Bay, Mainland, Orkney. 

 Lech, Voralberg, Austria. 



7. C. hostiana 



X 



C. demissa 



0% 



Loch Tummel, Perth. 



8. C. distans 



X 



C. lepidocarpa 



0% 



Totternhoe, Beds. 



(1) C, flava 



This rare British plant, with its specialised ecological requirements, seldom meets 

 the other members of the group in this country. However, at Roudsea Wood (Lancashire), 

 C. demissa occurs with C. flava, and there is a range of intermediate forms, which are 

 clearly of hybrid origin. These plants revealed a highly irregular meiosis, and the pollen 

 showed between 70 and 80 per cent sterility. It certainly seemed as if back crosses with 

 the parent species were present as well as plants, for there was a great range of forms 

 and it appeared that, in time, C. demissa would completely oust C. flava by hybridisation, 

 for the latter species was scarce compared with the abundance of hybrid plants and 

 C. demissa. This is the only record of a C. flava hybrid from this country; as this species 

 has never been found growing with or near C. lepidocarpa, C. serotina or C. scandinavica, 

 and as their ecological requirements are rather different, hybrids between C. flava and 

 these species seem unlikely to occur naturally. However, hybrids and back crosses 

 between this species and C. lepidocarpa were abundant by Lake Carezza in the Western 



