Page:VCH Cornwall 1.djvu/102

 A HISTORY OF CORNWALL Car ex liger ica, Festuca uniglumis, Sesleria ccerulea and Opbioglossum iiulgatum var. polyphyllum. Of these the second and third have yet to be sought out in other parts of Great Britain, and the sixth has only been found in one other county, viz. Norfolk. The Cornish heights are singularly unprolific. A few Batrachian Ranunculi and Utricularias in shallow pools, half a dozen or so local Carices on the windswept heaths, and the two species of filmy ferns are all they offer of interest to the collector. Sixteen of these hills run to over 1,000 feet, the highest, Brown Willy, 1,375 feet above sea- level. In the east the Cornish heights possess much of the wild grandeur associated with the Tors of Devon, but towards the west the chain becomes much interrupted and the hills lose elevation until at the Scillies the highest peak is only 220 feet. This goes far to explain the difference in the rainfall above mentioned. As the sources of the thirty-three principal streams the hills play no unimportant part in plant geography, for it is along the moist shady banks and at the estuaries of the streams that the most varied flora exists. The narrowness of the county pre- cludes the possibility of great rivers. Those at all deserving that name are the Tamar, draining 40 miles of the county, Fowey 30 miles, Camel 29 miles, Lynher 27 miles, Fal 19! miles, Inny 19 miles, Attery 14 miles, and the Seaton and Looe 12 miles each. With the exception of the Camel the principal streams run from the ' backbone' of the county to the south coast. Here again the result is two markedly distinct floras. The only sheets of water west of the Tamar approaching lakes are the Loe Pool near Helston, Dozmare Pool in the parish of St. Neot, Swanpool near Falmouth, and Hayle Kimbra on the Goonhilly Downs. Loe Pool is the only place in Cornwall where Corrigiola littoralis has been found, and the only British station for Nitella hyalina. Swanpool gives Chara aspera, C. bispida and C. canescens, while Hayle Kimbra gives C. aspera and its interesting variety desmacantha. Dozmare Pool has no attraction for the botanist. While the character of Cornwall has been much changed by culti- vation on the one hand and by mining operations on the other, not a single species of plant has suffered extinction by these causes. Those portions of the county which were marshes and bogs 100 years ago are for the most part in the same condition to-day, and the rarities which Ray and Turner and Jones found are still there. Along the coast also, where a continual fretting away of the cliffs is going on, and where the encroachment of the sands is becoming more and more manifest, the old species hold their ground albeit in some cases showing a diminution in the number of plants. Among the species which have become extinct through no other apparent cause than inability to retain a hold on the soil are Ranunculus circinatus, Mathiola sinuata, Hypericum linarifolium, Alth<za officinalis, Latbyrus maritimus, Potentilla argenfea, Pyrus domestica, Drosera anglica, Lytbrum Hyssopifolia, Diotis candidissima, Chenopodium bybridum, Urtica pilulifera, and Tricbomanes radicans. Corrigiola littoralis, once so abundant on the Loe Pool, has not been found there now for four 5