218 



KNOWLEDGE. 



[OCTOBEB, 1901. 



Fio. 2.— A Fruit of 

 the Musty Stork's-bill. 

 X 2. 



of the opening on its inner side already referred to. 

 Lord Avebui-y placed fruits of the Herb Robert, on his 

 biUiai-d-table. and found that the seeds were in this 

 manner projected to a distance of over twenty feet. 

 Fruits of this kind have been aptly named sling-finiits. 

 Nor is it beyond the powere of certain species to under- 

 take even the phmtinri of their seeds. The Stork's-bills 

 (Erodium). which ai-e closely allied to the Crane's-bills 

 or Geraniums, have curious fruits, each consisting of a 

 torpedo-shaped seed prolonged into a slender twisted 

 rod. which terminates in a long appendage set at right 

 angles to the axis of the remainder of the fruit. ■ The 

 seed is furnished with bristles pointing away from the 

 unattached end; and the twisted tail is hygi-oscopic — 

 very sensitive to moisture. Xow, if the seed be held 

 fast, and the whole moistened, the rod will untwist, and 

 as a result the free end will revolve like the hand of a 

 flock. But if, as will more likely 

 happen in nature, this revolution 

 causes the long appendage to come 

 in contact with some obstacle — a 

 blade of grass, for instance — then 

 the motion will be transferred to the 

 seed-bearing end, which will revolve 

 like an auger, and, as a result of the 

 lengthening caused by the untwist- 

 ing of the rod, the seed will be forced 

 intothe ground. Theupward pointing 

 bristles will come into play if the rod 

 dries again, tending to hold the seed down in its place 

 in spit« of the contraction, and to drag down the 

 opposite end instead ; another moistening will cause the 

 seed to buiTow deeper. A much simpler, but vei-y 

 pretty instance may be watched in the little Ivy-leaved 

 Toad-flax, a plant of the European continent which has 

 now spread over the greater part of the British Islands. 

 It grows on walls, and when in flower the prettv piu-ple 

 Snapdragon-like flowers stretch out towards the light 

 and air. But as the finiit ripens its stem bends towards 

 the wall, and seeks the deepest cranny it can find, in 

 which the seed may be deposited. ' Owing to this 

 arrangement, the fruit needs no winged appendage or 

 other device such as is possessed by so many wall plants, 

 to prevent the seed from falling uselessly to the in- 

 hospitable gi-ound below. 



Thus far regarding the dispersal of plants by means 

 of their seeds. We have not yet nearly reached the 

 hmit of power of spreading which our ■ wild flowers 

 possess, for vegetative reproduction plavs a most im- 

 portant part in this chapter of their life-historj-. We 

 may, if we wish, separate the latter processes into two 

 gi-oups, according as to whether the new shoot separates 

 from the parent plant, or remains, for some time at 

 least, attached to it. In aU cases it is of great im- 

 portance to note that reproduction of this kind is not 

 due to the nff.-<prhi,, of the plant, but to a portion of 

 the parent itself, which sooner or later commences an 

 independent existence ; it is due to a prolongation of the 

 life of a single generation, not the production of a new 

 generation. In some instances it is the new shoot alone 

 which survives from one season to the next If we 

 examine in autumn a plant of one of the Bladderworts 

 pretty floating plants with limp straggling stems and no 

 roots the stem will be found to terminate in a rough 

 egg-shaped knob. If we examine a plant in earlv spring 

 the stem is seen to arise from a similar knob " A root 

 less floating plant like this would get killed durin- the 

 winter by being frozen into the ice. so it concentl-ates 

 its vitality in these knobs— in reality, much compro=setl 



stems — which sink to the bottom, while the rest of the 

 plant decavs. and lie snugly there till spring, when they 

 rise again and send out fresh elongated stems, with 

 leaves and flowers. Similar winter buds, or hihemacula. 

 may be seen on the Frog-bit, certain Pond-weeds, and 

 other aqtiatic plaiits. In these cases the buds are 

 terminal, and represent the contracted stem, which 

 really grows on year by year, being elongated in stunmer, 

 contracted in winter. 



Bulbils are found on a variety of plants. Tliey are 

 little adventitious buds borne on the stems or leaves, or 

 in lieu of flowei-s, which sometimes remain attached to 

 the parent, sometimes drop off to commence at once a 

 separate existence. In the proliferous section of the 

 protean varieties of the Soft Shield Fern (Polt/ifirhuni 

 angulare). for instance, they may be seen crowded along 

 the rachis or midrib of the frond, and in a damp 

 atmosphere fomi a verdant row of little ferns before 

 the decay of the frond allows them to reach the ground 

 and take root. In the Lesser Celendine, again, little 

 egg-like, bulbils aie borne in the axils of the leaves; 

 they drop off and immediately commence life on their 

 o\vn account. Many of the species of Leek and Onion 

 (Allium) are conspicuously bulbiferous. the umbel of 

 flowers being crowded with little bulb-like buds which 

 sometimes altogether replace the blossoms. 



In the majority of instan'ces the increase of plants 

 by vegetative reproduction is accomplished by means 

 of the continued giowi:h of their stems, some or all of 

 which, instead of rising erect, creep on or below the 

 surface of the ground, giving off. continuously or at 

 intervals, roots below, leaves and flowers above, and 

 capable of quite indefinite extension — see the fii-st article 

 of this series (suprn, p. 27). The common Polypody 

 grows on and on year by year in this manner, the 

 hinder end of the stem dying by degrees. The Butter- 

 bur, whose great leaves form such picturesque masses of 

 foliage on our river banks, grows similarl}', with a stem 

 which pushes its way below the surface. Instances 

 where roots and shoots are produced only at intervals 

 are equally common — the Strawberry and Sitfast are 

 familiar examples. Underground stems of the same kind 

 are abundant. These it is that are so useful in binding 

 together shifting sands — stems like those of the Bent, 

 Lyme-gi'ass, Sea^sedge. The growth of the last-named 

 {Cnrff: nrenaria) is most interesting. On bare sandv 

 patches one may note the tufts of leaves and flowers 

 rising at regular inters-als in a straight line for several 

 yai'ds. Digging a few inches downwards, we discover 

 the connecting stem, running straight and level tmder- 

 ground, and terminating in a long point, white, polished, 

 and hard as ivory, which pushes its way ever fonvards 

 through the sand. 



Bramble-stems often form a high arch in the earlier 

 part of their yearly growth ; but in the autumn they 

 cur\-e earthwards, and the gi'owing point enters the soil, 

 where it roots and turns sharply upwards again. Next 

 year the arched stem flowers and dies, but a new plant 

 starts from the rooted tip : and so the bramble goes 

 looping along year by year. A few years ago I noted 

 a bramble-bush with rooted shoots averaging over 20 

 feet in length ; a calculation will show that in six years, 

 at the same rate of growth, a single bush might cover 

 an acre of gi'ound. 



The well-known " faii-y rings " of pastures are pro- 

 duced by the continuous growth of the mycelia. or webbv 

 underground stems, of certain fungi. These, starting 

 from one point, and spreading regularly, exhaust the 

 soil in which they live, so that as their area of growth 



