Ixxiv INTEODUCTION 



although the list of rarities is extensive. Eare and characteristic 

 species : — 



Thalictrum alpinum, 5. Orobanche rubra, 5. 



TroUius europseus, 3. Polygonum viviparum, 3. 



Saxifraga umbrosa, 11. Euphorbia Mberna, 11. 



Saxifi-aga aizoides, 5. . fEuphorbia amygdaloides, 3. 



Carura verticillatum, 6. Eriocaulon septangulare, 7. 



Ligusticum scoticum, 5. Carex Boenninghausiana, 2. 



Hieracium argenteum, 4. Elymus arenarius, 5. 



Hieracium sparsifolium, 3. Adiantum Capillus- Veneris, 6. 



Hieracium rigidum, 2. Cryptogramme crispa, 6. 



Hieracium auratum, 4. Aspidium Lonchitis, 6. 



Linaria repens, 5. Equisetum pratense, 3. 



36. Tyrone. 



North- central. Area 1260 square miles. Inland, with a few 

 miles of tidal water along the banks of the Foyle in the NW. A 

 large county, with many hills and much undulating ground. The 

 highest points lie along the northern margin (the Sperrin Mountains, 

 Sawell 2240, Dart 2040 feet) . In the centre Mullaghcarn rises to 1778 

 feet ; and everywhere but in the east, occasional hills rise to over 

 1000 feet. The geology of the county is very varied. The Sperrin 

 Mountains and a considerable area in the north are formed of meta- 

 morphic rocks. Elsewhere Old Eed Sandstone, Carboniferous lime- 

 stone, and volcanic rocks divide the honours, with Tertiary clays 

 fringing Lough Neagh on the east, and small ^Datches of Coal- 

 measures. The Foyle and Blackwater, which bound the county on 

 the NW. and SE. respectively, are the only rivers large enough to 

 possess a distinctive flora. The great Lough Neagh, the largest 

 sheet of water in the British Isles, fringes the division on the east 

 for nearly twenty miles ; the other lakes of the county are tiny. 

 Extensive low-level bogs are found around Lough Neagh. The 

 area of grass land is below the average — 43 per cent., and the area 

 under crops above the average — 30 per cent. Turf bog is repre- 

 sented by 5^ per cent., mountain land by 14 per cent. Our present 

 knowledge of the flora is almost entirely due to Miss Knowles, and 

 is tolerably complete. 



Flora 569 species, including a group of halophytes from the tidal 



