Mav, 190-2.] 



KNOWLEDGE 



115 



maiiiiiiiii. Las its Ikjiuu akmy the sen-coast. Most, as 

 already stated, are eoiispieiiously bvgrophile — lovers of 

 damp air. The Hard Feru and Lady Fern are con- 

 spiououslj calcifuge, the former especially jtining in a 

 limestone soil as rapidly as a Rhododendron; while the 

 Limestone Polypody, the Scale Fern, and Litstrea riijida 

 are particularly partial to limestone — strouijly ealcicolc. 



Our al])ine and arctic ferns are found chiefly in Scot- 

 land, the southern aud moisture-loving species in West 

 England and Ireland. The calcicole species exhibit 

 peculiarities of range. Lastini riijidu and Fdhjprdunii 

 Eohertian 11)11, which are locally abundant on the limestoue 

 pavements of northern England, being altogether absent 

 from the similar formation in Ireland, where, in the west, 

 their place is taken by the Maiden-hair. The rock-loviug 

 Ferns, especially the calcicole Scale Fern, have had their 

 range greatly extended by human civilization, on account of 

 the building of walls of stone and lime, which form for them 

 au eminently suitable home. But most Ferns are plants 

 of thoroughly wild ground, and decrease with the spread 

 of civilization. 



As regards their leafy parts, all our Ferns, with the 

 exception of the Adder's-tongue and Moonwort before- 

 mentioned, are arranged on a similar plan. A principal 

 vein or midrib traverses the whole length of the frond, 

 on each side of which the (>xpanded green lamina is arranged 

 symmetrically, the lower portion of the midrib being 

 generally bare aud forming a stalk (s(ipe]. On the under 

 side of the lamina the spores are produced. It is owing 

 to the cutting aud dividing of the lamina that our Ferns 

 possess so much variety. In one species — the Hart's- 

 tongue-the frond is undivided and strap-shaped; in the 

 Common Polypody aud Hard-fern it is divided into simple 

 comb-like teeth. In the Male Fern, itc, these pinnie are 

 again cut down to their midribs into jilnnuhs. And in 

 the Bracken, Lady Fern, and others the pinnules are in 

 their turn divided into lobi'n. The lower piuua; in many 

 species are the largest, giving the frond a triangular out- 

 line, aud in some, as the Oak Fern, the lowest pair are so 

 enlarged that the frond is ternate, consisting of three 

 divisions of nearly o(iual size. 



To return to the question of the reproduction of Ferns. 

 Although their tiny spores are produced literally by the 

 million, Ferus do not submit to artificial cultivation with 

 anything like the readiness displayed by Flowering Plants. 

 The reason is to be sought in their hygrophile proclivities. 

 To raise Ferus from spores, a continuously damp atmo- 

 sphere is necessary, and if the air is warm also, so much 

 greater the chance of success. But eveu then the diffi- 

 culties are uot over, for the oophore or prothallium genera- 

 tion is so minute that the seedlings run risk of being 

 smothered by the riih growth of algaj induced by the 

 confined atmosphere. Those Ferns which have creeping 

 stems may enlarge their area indefinitely by meaus of 

 vegetative gro^vth ; and in some abuormal cases, British 

 Ferns reproduce themselves by another vegetative process 

 — uamely by bulbils — little buds produced on some por- 

 tion of the frond, which grow directly into fresh plants. 

 Such bulbils are characteristic of many varieties of Polij- 

 stichum anyiilare, and occur, though more rarely, on 

 abnormal forms of the Hart's-tongue, Male Fern, Lady 

 Fern, &c. 



A much more curious and abnormal mode of reproduc- 

 tion has been brought to light in recent years. Let me 

 recall the normal process in our common Ferus. Spor- 

 angia, or cases containing spores, are developed iu groups 

 or rows on the uuder surface of the frond. The spores, 

 being liberated, give rise to small leaf-like prothallia, on 

 the uuder surface of which male and female organs 

 (antheridia and archegonia) are developed. When fertili- 



zation has taken place (which is effected by meaus of 

 motile autherozoids), vegetative 

 growth at once begins in the egg- 

 cell of the archegonium, and a 

 young fern is the result, the pro- 

 thallium withering away. In 1868, 

 a very beautiful variety of the 

 Lady Fern was found wild in 

 North Devon by Mr. K. Moule, in 

 which the fronds were large and 

 translucent, the ultimate divisions 

 being very long, slender, and 

 After deeply cut. The fern was ap- 



Fio. 4. — Prothalloid 

 bodiet occupying the 

 plaie of sponvngia in 

 Athyriiim FilixfiTinina, 

 da 



Dniery. Much enlarged, parently barren, for though jjlenty 

 of fructification was produced, 

 no spores could be obtained, and in consequence, in 1888, 

 only two divisions of the plant were in existence. In that 

 year, Mr. G. B. Wollaston discovered in another variety of 

 Lady iVrn, that the place of the spore-cases was occupied 

 by numerous bulbils, which were capable of forming new 

 plants by direct vegetative growth. Mr C.T. Druery was 

 led by this observation to examine the sporangia of var. 

 clarUsima, as the Devon form had been named, and found 

 that they consisted of groups of strange flask-shaped 

 bodies, which were quite unlike spore-cases. These were 

 carefully planted in a seed-pan ; they immediately com- 

 menced to grow at their tips, which expanded at length 

 into perfect prothallia, which in due course produced 

 male aud female organs, and subsequently young fern- 

 plants.* In other words, this remark al)le fern was 

 found to produce, not spore-cases and spores, but in place 

 of them prothallia, aud to pass from the asexual generation 

 (or fern-plaut) to the sexual generation (or prothallium) 

 without the intervention of the spore. Iu the year following 

 the annouucement of this discovery, a still more remark- 

 able phenomenon of a like nature was brought to mjtice.f 

 Mr. Wollaston observed an abnormal growth jjroceediug 

 from the tips of the pinnules of the Yuriety pidchet-ri ihuih 

 of Pohjgtichum a ngu tare— a,\so a North Devon find. 

 The tip was found to grow out into a delicate green ribbon, 

 which eventually expamled aud thickened into a fully- 

 formed prothallium, on which were developed archegonia 

 and antheridia. " This Polystichum," says Prof. Bower, 

 " is thus an example of the formation of an exj)ansion of 

 undoubted ijrothalloid nature bearing sexual organs, by a 

 process of purely vegetative outgrowth from the Fern- 

 plant — that is, there is a transition iu this case from the 



Kn;. 5.— Protlialloid body produced by outgrowtli of 

 veiulet of /". annulare, var. pidcherrimum, Wills. 

 After Druery. Enlarged. 



sporophore generation to the ooj>hore by a vegetative 

 growth, and without any connection with spores, or, 

 indeed, with sporangia or sori. It may be regarded as 



• Druery in Journ. Linn. S^c, Botany, \o\. X.X.I. t iiower, ibid 



