January 1, 1890.] 



KNOWLEDGE 



43 



weather comes round and wakes them mto renewed 

 activity, and enables them to complete their cycle of 

 chanf,'es. The flea, then, is an insect with a complete 

 metamorphosis, therein differing in totn from both the bed- 

 bug and the cockroach, and agreeing with dipterous flies 

 in general. 



Pleas do not seem to be confined to human habitations ; 

 there is a common belief that sandy seashores are infested 

 by them, and that visitors to such spots may expect to 

 return home " with company." In support of this notion 

 may be adduced a statement made by Mr. T. .1. Bold 

 before the Tyneside Naturalists' Club about twenty-tive 

 years ago, to the efl'ect that he saw fleas "dancing about 

 quite merrily between Hartley and Whitley, and at other 

 times they have been noticed quite frequently from South 

 Shields to Marsden." There are, no doubt, many fi'ag- 

 ments of animal remains scattered about amongst loose 

 sand, such as would serve very well for the larvre to prey 

 upon ; but what the perfect insects can find to live upon in 

 such situations is a mystery, for it can hardly be main- 

 tained that they fi'equent the spot with a view to possible 

 human visitors. 



That fleas can be excluded from houses by the use of 

 odoriferous plants has long been a firmly believed tradi- 

 tion ; witness the name of our common wayside plant, 

 the Fleabane. The smoke of this when burnt was held to 

 be particularly distasteful to fleas, which would forthwith 

 abandon any premises in which they detected it. Several 

 species of Composita> have been credited with this potency ; 

 a preparation made from the leaves of a Pi/ivtlirum from 

 the Caucasus was at one time extensively used in Eussia 

 for drivmg away fleas. Wormwood (Artemisia) also was 

 believed to possess similar powers, and Tusser has the fol- 

 lowing lines in illustration : — 



While wormwood hath seed, get a handfull or twaine. 

 To save against March, to make flea to rcfraine ; 

 Where chambere is swecpod and wormwood is strown. 

 No flea for his life dare abide to be known. 



The " sweeped chambere " bad no doubt quite as much to 

 do with the matter as the wormwood. In folk-lore the 

 first of March is ultimately associated with fleas. It is 

 still a practice in Kent to keep the doors shut on that day 

 to prevent the fleas from entering, and in Sussex the door- 

 steps are swept on the same day for the same purpose, and 

 thus it is believed that immunity fi'oin their attacks will be 

 secured for a twelvemonth. 



(I'n /.,' cnlllilllUil.) 



THE LIFE-HISTORY OF A FERN. 



I'>v E. JIansei, SvMi'soN, M.A., M.I). Cantab. 



M 



OST people like ferns, and now-a-days so many 

 people keep them that a brief sketch of the life- 

 history of a fern will probably possess interest 

 for many readers of Knowledge. Ferns be- 

 long to the great group of Cryptogams. They 

 owe; that name to the fairly obvious fact that in them the 

 organs of reproduction are not so visible, at all events at 

 first sight, as is the case with the Phanerogams or 

 flowering-plants. Another title must be added on to that 

 of C'ryptogams, to narrow it down to our more immediate 

 subject. That w^ord is " vascular " ; by it we mean that these 

 plants have fibro-vascular bundles in their steins, leaves, 

 and roots (tliat is to say, supporting fibres and vessels 

 which serve in pnrt for transmitting nourishment from 

 one portion of tlie plant to anotlier). But our " division " 



must go farther, for the vascular Cryptogams are di\ided 

 into Filicinfe (ferns and rhizocarps), Eqrusetineae (the 

 Horsetail group), and Lycopodinea?. Beginning, then, with 

 a mature fern, we notice the little brown patches or streaks 

 on the under surface of the fi-onds of many fems, such as 

 the Male Fern, the Hart's-tongue, the Polypody or the 

 Maidenhair. These are called sori, and consist of masses 

 of little capsules — the sporangia — made up of a thin 

 envelope of cells, save at one part where a thickened band 

 (sometimes merely a small accumulation, as in the 

 Osmunda Fern) extends almost round the capsule. Com- 

 pare one of these sporangia with one of those watches with 



Fig. 1. — Section TURouon a Sorus. 

 a, Cap or Indusium : R^ Sporangia ; 

 y, Fibru-vascular bundle ; g. Green 

 parenchyma ; ^ Epidermis or skin. 



Fig. 2. — Pbotiiallium. 



a^ Archegonia ; ft_ 



crystal faces and backs which were popular a few years 

 ago. The crystal portion will represent roughly the thin- 

 walled part of the sporangium, while the metal rim run- 

 ning round between the two plates may serve to indicate 

 the position of the annulus, or tliickened band of cells. 

 These sporangia, as you might guess from the name, con- 

 tain the spores, and the armulus plays a very important 

 part in the eviction of these spores, ^^■hen they are ripe, 

 the ring contracts under certain conditions of the atmo- 

 sphere, and, as the band is not complete, it tears the 

 thin coat of the cells apart, and turns the spores out in 

 to the world with considerable violence. In some instances 

 these sporangia are covered by a kind of cap, called an 

 indusium, which assumes varied forms ; but sometimes it 

 is absent, as in the case of the common Polj-pody. In 

 each species of fern the spores are all of the same size, 

 and all of them produce, when germinating, almost 

 identical results. This fact, besides others relating to 

 their growth, &c., serves to mark ofl" ferns fi'om the neigh- 

 bouring order of Rhizocarps, in which there are two kinds 

 of spores — macro- and micro-spores — and the product of 

 germination of a large spore differs greatly and invariably 

 from that of a small one. Returning to the fern spores, 

 we notice that they are irregularly shaped bodies, gene- 

 rally dark-brown in colour, having a thin inner coat and 

 a hard and thick outer one. The latter is useful in pre- 

 venting extremes of weather and temperature from injuring 

 them, and perhaps also in protectmg them against the 

 attacks of insects. When the spore has found a suitable 

 resting-place, on a damp surface, with suflicient light and 

 air and warmth, it begins to germmate. It sweDs up, 

 and puts out a prolongation like a finger, covered by its 

 inner coat, through an aperture in the outer coat, much 

 in the same w-ay as the pollen tube is protruded from the 

 pollen-grain. This finger grows and broadens into a 

 heart-shaped mass, a plate one cell thick, of green uniform 

 cells, containing chlorophyll, and this it is which is com- 

 monly Imown as the prothallium of the fern. A very good 

 idea of its appearance can be obtained from the common 

 liverwort {Munliinitin I'dli/iiKn-iiliii) so frequently found in 

 damp court-yards. On the under surface of this pro- 

 thallium, just behind the notch wliich gives it its heart 



