50 



KNOWLEDGE, 



[March, 1902. 



or //icroKi/j/iiVc*!— find a suitable abode. An insular area, 

 on the otlior liaud, affected by the comiiarativcly constant 

 1eni]iorature of the surronndin«j ocean, exhibits a more 

 cfjuable climate, and hero the second class — cold-fearers, 

 or /;-i(/o/h<7c«— will congregate. While, in comparison 

 with most parts of the European continent, the British 



'■ Oh ! to bo in Enjjland 

 Xow that April's there " 

 A tjpical Cool-temperate plant association — B-n-ard-forming 

 grasses and low herbaceous plants, with groups of deciduous trees. 



Isles possess an insiilar climate and a frigof uge flora, we 

 may trace within our area considerable variation in this 

 respect. Thus, the east of England, when com])ared with 

 west, or nmch more with the west of Scotland or Ireland, 

 has a continental climate. The annual range of tempera- 

 ture in the eastern counties of England is nearly double of 

 that which obtains on the west coast of Ireland or the 

 Outer Hebrides. And another question is bound up with 

 this one. An insular climate is characterised by a moist 

 atmosphere, the result of proximity to the sea ; the 

 continental climate by a drier atmosphere. Plants exhibit 

 marked profei'ences in respect of aerial moist u it. some 

 favouring the dampness of an insular climate (hygrophiles), 

 some the dryness of a continental (xerophiles). In the 

 British Isles the thermophiles and xerophiles reside largely 

 in the dry sunny eastern counties of England, while the 

 frigofuge and hygrophilous species increase westwai'd. 

 These two groups, in fact, constitute in great measure 

 H. C, Watson's "Germanic" and "Atlantic" types of 

 distribution, the one characterised by its increase in the 

 east, the other in the west of England. As we go north- 



wards, likewise, into the colder and wetter regions of 

 Scotland, the East-England group dies out, and is, in the 

 extreme north and on the hills, at length replaced by 

 various species of the Arctic-Alpine flora, which are 

 essentially hygrophilous, though not frigofuge. These 

 beautiful little northern and alpine plants arc accu.stoined 

 to a damp air, little sunlight, and a soil wet yet thoroughly 

 drained — facts to be remembered in our attempts to grow 

 them in our gardens. 



But there are many species sufiSciently plastic in their 

 constitution to accommodate themselves to every variety 

 of climate to be found in Britain. These widely distri- 

 buted species constitute the "British type" of H. C. 

 Watson. Some of them even range from the summit of 

 the highest mountain of northern Scotland to sea level in 

 the south of England. Most of them are characteristic 

 members of the Cool-temperate flora. 



When we come to consider the flora in greater detail, 

 wide diversities of vegetation become at once apparent, 

 and these, as already stated, are due largely to differences of 

 moisture and soil. On a great turf -bog, for instance, where 

 the supply of water is equal, and the soil everywhere the 

 same, an almost absolute uniformity of flora exists, some- 

 times over thousands of acres. But usually our country 

 exhibits considerable diversity of flora even within limited 

 areas — the plant-associations characteristic of meadow, 

 wood, marsh, stream, and gravelly or sandy wastes, com- 

 pared with which agreeable variety the uniform, though 

 often rich and beautiful flora of the veldt, prairie, savannah 

 or steppe were monotonous. The effect of this diversity of 

 conditions is that, from the point of view of any one of 

 the constituent plant-groups, the country consists of a 

 sprinkling or network of oases set in a desert — an 

 archipelago, in fact. The major portion of the surface of 

 our Islands consists of dry ground capable of producing 

 crops of the plants useful to man, and has, a% a matter of 

 fact, been tilled for many hundred years. To the effect of 

 tillage in destroying the natural plant-associations, 

 reference was made in a previous article, where also the 

 converse result of man's operations in introducing alien 

 plants was enlarged upon (pp. 16-19 supra). But the bulk 

 of the native plants of ordinary soils — mesophytes as they 

 are called, from their requiring a moderate supply of 

 water — still hold the ground in lessened numbers, and are 

 widely spread, since the area suitable for their growth 

 stretches continuously, forming, indeed, the sea in which 

 the islands of very wet soils or very dry, of very limy soils 

 or soils devoid of lime, are set. The Daisy, Bramble, 

 Honeysuckle, and Ribwort Plantain, for instance, spread 

 continuously over the surface of our country, and easily 

 avoid the only barriers — the higher mountain-chains — 

 which might impede their progress, by out- flanking them. 

 It is different, however, in the case of hydrophytes and 

 xerophytes — water jdauts and desert plants. Take the 

 case of one of the common Pondweeds — say Poftniingcfim 

 lucenn or rufcscenx. These plants grow in water, and 

 need this medium continually round them ; their flowers 

 alone rise above the surface, in order that the good offices 

 of the wind may be utilized for effecting cross-fertilization. 

 Lakes are their favourite habitat, they dislike flowing 

 water, and more still rapid alterations of level, so 

 that we seldom see them in rivers, or in dams or 

 reservoirs. How are plants such as these to spread ? The 

 question may well give us pause. Their seeds* are too 

 large and heavy to lie borne by the wind, even if 

 they ripened above the water, which they do not ; 

 and if entrusted to the stream which presumably drains 



* I use the word "seed" in its popular sense- 

 ot dispersal." 



' a one-seeded unit 



