POLTPODIUM VULGARE 



Rhone Valley in Switzerland at the eastern end of the Lake of Geneva at an elevation 

 not exceeding 400 m., at Dartmouth in south Devon, abundantly in the Cheddar Gorge 

 and some other limestone habitats in Somerset, on Ingleborough in Yorkshire and in the 

 Burren in the west of Ireland. It may confidently be expected to occur in central 



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Fig. 132. Sporangium of tetraploid Po/;'/^o</2wnz from 

 Cumberland showing twelve indurated cells in the 

 annulus, from a glycerine jelly mount, x 100. 



Fig. 133. Sporangium of diploid Polypodium 

 from Cheddar showing five indurated cells 

 in the annulus, from a glycerine jelly mount. 



X 100. 



Fig. 1 34. Sporangium of hexaploid Polypodium from Anglesey showing approximately nine indurated cells 



in the annulus, from a glycerine jelly mount. 



X 100. 



Europe, and profitable places to look would be the Biscutella districts in the river valleys 

 of the Rhine, Elbe, Oder and Danube, but until these have been sampled the eastern 

 limits of this 'variety' cannot be determined. 



The morphological characteristics of the diploid can best be appreciated by a glance 

 at Figs. I30fl, b, 131 a and 135 a. The most striking character is the oval frond which 

 even in small specimens widens out disproportionately much in the centre compared 

 with the tetraploid. Another detail which not all leaves display but which can generally 

 be found in some leaves on every plant is that the two lowest pinnae often project sharply 

 forward in the manner so characteristic of the Beech Fern {Phegopteris) . This character 



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