THE GENUS EQUISETUM 



spores, and although Milde began to doubt this diagnosis in later life owing to the in- 

 crease in the number of recorded localities, his original reasons are still valid. The 

 abortive spores in themselves suggest hybridity even more clearly to us than to a 

 botanist in Milde's day, and the morphology of the plant is not only intermediate be- 

 tween the two suspected parents but ranges rather widely between the two extremes in 

 different localities, thus suggesting that it is either re-formed from time to time from 

 different strains or that a limited degree of fertility exists in it and therefore some 

 genetical segregation. 



I am indebted to Dr Praeger for supplying me with the distribution map shown in 





'y^ 



J*>r 



£. /imosum n = 108 



Fig. 223. Explanatory diagram to Fig. 222a. 



Fig. 225, which indicates that E. litorale is scattered widely over Ireland with a frequency 

 which bears some relation to the closeness of sampling; the abundance of localises in the 

 Belfast area, for example, being probably diagnostic of the alertness of the Belfast 

 Natural History Society rather than denoting an actual preference for this region. 

 Living material from two sources was sent to me. In one, which came from Galway Bay, 

 partially expanded cones much resembling E. arvense but with wholly aborted spores 

 were too old to investigate. The second specimen came from eastern Ireland and grew 

 for many years in cultivation, but gave only sterile shoots much resembling E. arvense 

 in appearance. A visit to the wild locality of this material in June 1938 with Dr Praeger 

 showed it (Fig. 224) to be in habitat an aquatic plant as is E. limosum, though with 

 a solid branched stem like E. arvense. The cones were, however, borne exclusively on 

 the ends of the current green shoots as in E. limosum. From these, successful fixings 



MPC 22^ ^•' 



