40 



Proceedings of the Royal Irish Academy. 



•weed segregates. The restricted range of plants of this and the follow- 

 ing groups (arising from the more restricted area by which the types 

 are defined) as compared with that of the " Central " and "Marginal " 

 plants, is evident from the fact that the average number of divisions 

 pfer species drops to 6, as compared with 15 and 16 in the two preced- 

 ing types. 



Fig. i2.—Saxifraga opposiiifolia. 



Fig. 33. — Circcsa alpina. 



Fig. 34. — Cicuta virosa. 



Fig. 35. — Potavwgeton filiformis. 



The distribution of four selected examples of this type is shown ia 

 figs. 32 to 35. All of these are comparatively wide-ranging species, 

 but many plants of the type have a quite limited range, mostly with 



