Cavan Botany
The Silurian area. One of the largest areas of uniform character to be found in Ulster is the undulating tract occupied by Silurian slates which includes the greater part of Down, Armagh, Monaghan, and Cavan (Bed and Breakfasts, Cavan, Ireland), and only gives way to the prevalent limestone of central Ireland when it reaches the banks of the Shannon. This area is usually hillocky, covered with boulder-clay, and highly tilled. For the botanist interest centres in the lakelets and marshes which occupy the innumerable hollows.
In these Callitriche autumnalis, Cicuta virosa, Polygonum minus, Rumex Hydrolapathum, Typha angnstifolia, Sparganium affine, Butomus umbellatus, Potamogeton obtusifolius, Isoetes lacustris, are characteristic species. The flora is richest in eastern Down, where, perhaps partly on account of a slight admixture of lime in the drift, certain marsh and water plants from the Central Plain creep in. The hydrophile flora of this area includes, in addition to the above-named, Hottonia palutris, Elatine Hydropiper, Ceratophyllum demersum. Nasturtium sylvestre, Stellaria glauca, Juncus obtusiflorus, Potamogeton plantaginens, Carex teretiuscula, C. filiformis. The first of these has here its only Irish stations. The second is extremely rare in the British Isles. Most of the rest are abundant Central Plain species, but unknown elsewhere in the north-east.
