Holly FernHOLLY FERN OR ROUGH ALPINE SHIELD FERN
The Holly Fern or Rough Alpine Shield Fern is a rigid and prickly-looking plant, whence comes its English name. The fronds grow in a tuft from the extremity of a very slowly lengthening rhizome. The size of the fronds is very variable, from a few inches to a foot and a half in height; they are generally of a rigid texture, but this depends greatly on situation; sometimes they are thinner and spreading, or even almost pendulous.
The colour is of a deep glossy green in the Irish and Scotch specimens, while in the English and Welsh it is duller; and the whole plant is not so prickly and holly-like as in the Irish and Scotch plants. The margin of the fronds is set with spinous teeth. The sori are circular, disposed in long series on each side of the mid-rib, and often become confluent in maturity.
This rare fern seems to have been very familiar to older botanists and herbalists, and is frequently mentioned by Ray, Gerarde, and others. It is exceedingly difficult of culture, and even when established, is often disappointing to the cultivator; for it is only seen in perfection on its native rocks, in the open air in Ireland, Scotland, or Wales. In the south of England it seldom thrives, and, on this account, is best left out of a growing collection of ferns.
The groups of ferns now called Nephrodium was formerly known as Aspidium, afterwards as Lastrea - but we have adopted the most recent name according to modern botanists. Its distinguishing characristic is a notch in the otherwise round involucre which changes the simple circle into a heart or kidney-shape. Many of the largest and most elegant ferns belong to this group. Nephrodium is from a Greek word signifying kidney, in allusion to the form of the involucre.