In open country, by roadsides and streams, and covering hillsides, a great variety of ferns is found. The ubiquitous bracken, Pteridium esculentum, the farmer's misery, grows to 6 ft in height and spreads rapidly by means of rhizomes. These are starchy and were used by the Maoris both as food and as medicine. The lace fern, Paesia scaberula, is less troublesome but may over-run considerable areas; it is light green, sticky, with finely cut fronds. Histiopteris incisa is a large wayside fern. Particularly in the south it grows with the tall Hypolepsis tenuifolia and the smaller H. rugosula. On roadsides, as well as in forests, is found the large tufted Cyclosurus penniger. In swamps in the North Island are Thelypteris palustris and three species of Cyclosurus. C. gongylodes is common near thermal springs. These latter are commonly known as species of Dryopteris. Cystopteris is a genus of small ferns with pale membranous fronds found throughout the country in dry open places, in clefts of rock, and in mountain districts. Three species of Lindsaea of the family Pteridaceae are L. viridis, a beautiful little fern with narrow, pale green fronds, found on the banks of streams; more widespread, especially in the North Island, is L. trichomanoides, with golden brown stems, found in dry places; and L. linearis, with small, narrow fronds, found amongst the manuka and light scrub in many localities. There are two species of Pellaea, of which P. rotundifolia is usually regarded as a drought-resisting fern and is very common, but P. falcata, of similar dry habitats, is comparatively rare.