October, ICOl.] 



KNOWLEDGE. 



211) 



expands, the central portion keeps dying off, and a 

 slowly enhu-ging ring of gi-owing fnngiis results. The 

 visible effect produced is due to the fa^ct tliat the plant 

 acts injiu-iously on the sun-ounding vegetation, pro- 

 ducing a withered ring where the fungus is growing. 

 But inside of this is a ring where both the fungus and 

 its victims have died, and on the soil thus left un- 

 ton.-inted, and enriched by the dead vegetable matter, a 

 luxuriant vegetation has sprung up, which catches the 

 eye. Rings fonned iu a similar manner, bv steady out- 

 ward growth ,-ind the dying off of the older central 

 portions, may be not unfrequently ob.=ervcd among the 

 liigher phoiits. 



Roots also lend themselves sometimes to vegetative 

 reproduction, producing leafy shoots, which become in- 

 dependent plants. The White Poplar is often sur- 

 rounded by progeny of this kind, and the Sea-Buckthorn 

 covers large areas of sand-dunes by the same means. 

 Tubers, such as those of the potato, are also really stcm- 

 structirres produced by the roots. 



Having thus briefly reviewed the various modes in 

 which seed is dispei-scd and scattered, and also those bv 



Fig. .3. — A Stiuly in Gregarious Plants -Winter lli-liolropi', Eamsons, and Ivy 



which vegetative reproduction is carried on, we are now 

 in a position to study the distribution in any given area 

 of the various species which compose its vegetation, so 

 far as this is the result of its methods of reproduction. 

 In the case of plants which produce flying fruit, we 

 should expect to find the individuals very widely spread, 

 and generally growing singly, in open situations such as 

 these species affect, where in turn their flying fruit may 

 be freely exposed to the wind which will bear it away. 

 Plants of which the fi-uit is eaten by birds should like- 

 wise have a wide distribution, and we might pc'rha])s 

 especially expect these about bushes and hedges, wherein 

 birds would perch or shelter. Where no devices exist 

 for a wide dispersal of seed, we might look for a more 

 social grouping of individuals, in little colonies, or 



dotted over larger areas. And in the case of plant.s 

 which can increase by means of their creeping stems, we 

 might often expect to find dense growths, and if I may 

 use the expression, populous cities. At the same time 

 it must l)o remembered that all sorts of other conditions 

 and requirements exist simultaneously tO' modify or 

 obscure such groupings; but the general .application of 

 these niles will at once be observed by (ho lield-botanist. 

 Our common thistles, for example, have flying fniits ; 

 furthermore, their formidable armour of spines i-cnders 

 them invulnerahlo to grazing animals; lieiue wc find 

 them scattered far and wide over the pastures. The 

 Field Thi.stlo has far-creeping underground stems; hence 

 it forms dense patches, almost impossible to eradicate, 

 while the Spear Thistle and Marsh Thistle, destitute of 

 creeping stems, rise singly. The Wood Anemone, grow- 

 ing in shady places, could not use flying seeds to ad- 

 vantage; the seeds are devoid of means of wide dispersal, 

 and the stems creep ; both causes combine to make the 

 plant grow in the lovely dense sheets of tender green 

 dotted with white flowers that wc know so well. Its 

 ally, the Pasquc-dowcr. on the contraiy, lives on the 

 open downs. The stems do not 

 cree]i, the fruit is formed for 

 wind-carriage; in consequence we 

 find the plant dotted here and 

 there over wide areas. Mo,st of 

 our wild flowers which have bul- 

 bous " roots " produce young 

 bulbs as offshoots of the parent 

 ones, thus tending to establish 

 dense colonies — note the profusion 

 in which the Wild Garlic (Fig. '-i) 

 and the Wild Hyacinth grow. 

 Many of our marsh and water 

 plants have creeping stems, 

 which tend to produce striking 

 masses of vegetation — wit- 

 ness the miniature forests of 

 the Reed, Bulrush, Reed- 

 mace, or Sedge which fringe 

 the ponds and lakes, often 

 so dense that no other plant 

 can obtain a footing among 

 them. Certain common land 

 ]ilants with creeping stems and 

 large leaves, such as the two 

 more familiar species of Petasites 

 — the common Butterbur and 

 the Winter Heliotrope (Fig. 3) — 

 form such dense masses of foliage 

 as to effectually choke off and kill 

 all other plants on the area which 

 they invade. On the hill-sides, two 

 of our most strongly social sj ecies 

 — the Heather and the Bracken — often come into sharp 

 contest, each holding undisputed sway over certain areas, 

 with a border-line where no doubt a keen stniggle is 

 continually going on — the Bracken having the advantage 

 of creeping branching rhizomes or underground stems, 

 and tall dense growth which overshadows its rival ; the 

 Heather on its side being possessed of great vitality and 

 fertility, and perhaps other less evident advantages, 

 which enable it to hold its own. 



But as we have said, many other factors are at work 

 influencing the distribution of plant life — questions of 

 soil and of situation; of water supply, and the supply 

 of air and light; and there is the keen struggle for 

 existence between plants of similar proclivities, and a 

 complicated and incessant, action and rea 'tion not only 



