58 



J. P. PUGH 



Wide variation occurs throughout this species, and the most reliable character 

 seems to be the large number of ramenta on the rhachis. It has been known for some 

 time that the fronds of D. horreri tend to overwinter whereas those of D. filix-mas do 

 not, and this characteristic is obvious in winter when green plants of D. horreri are most 

 prominent amidst brown, tangled remains of D. filix-mas. - 



In spring, the indusial character, as shown in fig. 2, is unmistakable, but this 

 condition does not persist for long. 



Fig. 2. Surface views and diagrammatic longitudinal sections of the sori of D. horreri (left) and D. filix-mas 



(right) (X 20). 



The truncate nature of the pinnules is sometimes very marked, but a gradation 

 series between the truncate form and the tapering form characteristic of D. filix-mas 

 has been observed. However, in specimens of D. horreri which exhibited more or less 

 tapering pinnules, the periphery of the pinnules was more entire and less toothed than 

 comparable pinnules of D. filix-mas. 



D. horreri has been described as yellow-green in colour (Xewman, 1854, 191; 

 Warburg, 1952, 38). Manton (1950, 54) records it as often more yellow-green. Material 

 is abundant in the British Isles and on the continent which is definitely dark green. 

 Therefore colour is not a reliable diagnostic character and conditions affecting the colour 

 are being investigated. 



Information regarding the distribution of D. horreri in the British Isles is still very 

 incomplete and any records of localities would be most welcome, especially from Ireland. 

 The inclusion of a small note regarding topography and geolog>^ (where possible) would 

 also be useful, as these will greatly assist in the determination of ecological requirements. 



Distribution 



The following list shows the records as they are known at present; it is composed 

 of all the localities for which there is an herbarium specimen ; these localities arc represented 

 on the map (fig. 4) as solid dots. The open circles on the map represent all the 

 localities mentioned in the literature and a list of these has been deposited in the Crypto- 

 gamic Room of the British Museum (Natural History). I am indebted to the following 

 for personal communication of several localities : — D. E. Allen, O. Buckle, J. G. Dony, 

 Miss E. J. Gibbons, J. D. Grose, J. W. Hcslop-Harrison, H. A. Hyde, R. M. Payne, 

 H. Milne-Redhead, Miss C. M. Rob, W. A. Sledge and A. E. Wade. 



