September, 19 17. The Irish Naturalist. 141 



EOUISETUM LITORALE IN IRELAND. 



BY R. LLOYD PRAEGER. 

 (plates VI., VII.) 



The Rocky River, in the ^lourne Mountains, above the 

 point where it joins the infant Bann, is a pleasant trout- 

 stream, babbhng among granite boulders or pausing in 

 sandy pools. The banks are rough, rising steeply for a few 

 feet, amid a tangle of willows, gorse, and rocks, with an 

 undergrowth of rushes, Molinia, &c., and then spreading 

 out into heathy land, sheep pasture, or tilled ground. 

 Among the plants which fringe the stream. Horsetails are 

 conspicuous by their abundance and variety. Five species 

 can be readily distinguished — E. hyemale, E. sylvaticum, 

 E. palustre, E. limosum and E. arvense. The first keeps to 

 the steep overhanging edges of the banks, and is widely 

 spread along the stream. The second, the most pleasing 

 of British Horsetails, is very abundant, and like the last, 

 displays no noteworthy variation. E. palustre is rare, but 

 grows in profusion at one place — a compact erect plant, 

 with short branches and large black cones. With it the 

 unbranched form — " var." midum — and other variants also, 

 occur. E. limosum is seen only occasionally — the un- 

 branched form here and there in pools in the stream, 

 rather dwarfed in stature ; and the branched form — " var." 

 fluviatile — well developed and two feet or more in height — 

 in a couple of riverside ditches. Lastly, E. arvense in its 

 typical form keeps to the drier ground — sandy overhanging 

 river-banks and adjoining earthen fences, growing half-a- 

 foot to a foot long, and, as usual, varying considerably as 

 to size, habit, and branching. At the time of our visit, 

 in the middle of last June, the fertile stems had already 

 quite passed away, and the barren ones were fuUy 

 developed. 



