xxxii INTEODUCTION 



into heath, with Bracken, Gorse, Orchids, and Cudweeds. As we 

 ascend, likewise, their flora changes, and eventually alpine plants 

 make their appearance. 



Plants of the Marshes. — The marsh plants do not form so dis- 

 tinct a group as those of the bogs, since many of them likewise occur 

 along the margins of lakes and rivers, where the conditions are similar. 

 In the Central Plain considerable areas may be generically de- 

 scribed as marsh, varying in character from wet meadows or wet 

 clayey pasture to silted up lakes or deep swamps. Frequently the 

 soil consists of a soaking sticky clay, limy and sterile, but sometimes 

 covered with a congenial layer of vegetable mould. In such marshes, 

 amid broad patches of Juncus ohtusiflorus and Phragmites communis, 

 Cladium Mariscus and Carex filiformis may be expected, and among 

 the undergrowth Efipactis pakistris and Galium uliginosum are 

 characteristic ; and where a few inches of water lie, Utricularia 

 intermedia, Potamogeton plantagineus, and Chara polyacantha. are 

 almost sure to be found. Of the above, Cladium, C. filiformis, and 

 TJ. intermedia increase westward, and are in no way affected by 

 the absence of lime ; the others range chiefly over the Limestone 

 Plain. 



"Where marshy meadows stretch, such as the extensive "callows" 

 along the Shannon, a more varied and attractive flora prevails, 

 and the landscape is brightened by patches of Thalictrum fiavum, 

 Lysimachia vulgaris, Carduus ])ratensis, with abundance of Meadow- 

 Sweet and Purple Loosestrife, and more locally Latliyrus palustris, 

 Galium boreale, and rarer plants, amid a profusion of Orchids. 



Plants of the Riyers. The Shannon. — The only Irish river that 

 can be said to possess any marked peculiarities in its flora is the 

 Shannon, which is interesting in several respects. It is the largest 

 river in the British Isles, and 214 miles in length. From its source 

 among the Cavan hills it descends 186 feet in ten miles to Lough 

 Allen. There it enters the Limestone Plain, and flows southward 

 across it for some 130 miles. Its fall in this distance is only 51 feet, 

 and the river forms at intervals great lake-like expanses, with 

 winding shores and numerous islets, being in places four to seven 

 miles wide. From Killaloe, at the southern end of Lough Derg, 

 the Shannon cuts its way out of the Central Plain through high 



