_Cystopteris fragilis._ The generic name of this Fern is formed of the two Greek words _kystos_, “a bladder,” and _pteris_, “a fern.” The specific name is, of course, a Latin word which means “easily broken.” The Brittle Bladder Fern. This is one of the most beautiful of all our native Ferns. From a tufted root-stock which is clad with pale brown scales the fronds arise; these are about six or eight inches in length and are lanceolate in outline. This Fern has a habit of spreading in such a way, that each plant may have several of the tufted crowns from each of which arise a cluster of fronds. These are sometimes once, and on other occasions, twice pinnate. The pinnæ are about an inch in length, and where there are pinnules these are toothed. We shall find the sori on veins which run from the mid-vein of the pinnules. The spore patches are rounded and are covered with a curious indusium, with an inflated appearance towards the centre. It is from the resemblance of this indusium to a bladder that the plant has received its popular name. With the disappearance of the indusia the sori tend to spread over the whole surface of the back of the frond. The general appearance of the Brittle Bladder Fern is of a delicate nature and it has a very distinctive appearance. [Illustration: Cystopteris fragilis. The Brittle Bladder Fern.] Properly speaking, the Brittle Bladder Fern is a mountain species, though it sometimes occurs on old walls or in rocky clefts which are not very elevated. The species is widely distributed in all parts of Great Britain, though in frequented districts it is soon exterminated. The Brittle Bladder Fern does not seem to grow very well in the open rockery, though it is fairly easy to cultivate in pots. The fronds die down at the approach of winter. There are a certain number of varieties. _Cystopteris montana._ Here the specific name is formed from the Latin word _mons_, “a mountain.” The Mountain Bladder Fern. This is the only other recognized species of Bladder Fern to be found in the United Kingdom. The species has a slender creeping underground stem from which arise the delicate fronds. These are usually about four to eight inches in length, and the stipes is considerably longer than the leafy portion. The design of the frond is rather like that of the three-branched Polypody, this being due to the fact that the lowest pair of pinnæ is much larger than any of the others. The general outline of the fronds is wedge-shaped, and these are very finely divided. Indeed in a well-developed leaf the fronds may be three or even four times pinnate. The pinnules themselves are also deeply cut. It will be noticed that the lower portion of the frond is always more freely divided than the upper part; a common characteristic in Ferns. The sori are very freely scattered on the lobes or pinnules at the back of the frond, and these are covered with the curious hooded indusia which were noticed in the last species.