-36 



HINTS AND NOTJsS 



should nexl be stucliccl as in a nu-adow, since I case of a meadow or pasture, the dennite 

 (irasses are here allowed to tjrow. Tile ditch occurrence of cornfield plants being especially 



shoiilil be also treated as in 111 



lied. 



SECTION IV 



Till': .si<:a-coast 



Zonal Character of the Coastal Vegetation. — 

 The xetji-lation u\' tin- sea-coaNl diUns from 

 every other type of ve'^clation in that it is 

 entirely restricted to the junction of the sea 

 with the land. This causes at once a more 

 or less uniform altitude, the sole diflerence in 

 this respect beini;; defined by the rockiness 

 or otherwise of the seaboard. Thus the mari- 

 time plants are at once confined to a fringe 

 along the coast of little extent, rarely en- 

 croaching inland more than half a mile, or a 

 little more where salt marshes, which are 

 secondar}' products of the coastal vegetation, 

 are concerned. It is, in fact, the marginal 

 action of the sea, with its saline waters and 

 peculiar deposits, that deternrnus the forma- 

 tion of maritime vegetation. 



There are two limits to the action of the 

 sea, high-water mark and low-water mark, 

 and as regards flowering plants these have 

 little or no etTect upon distribution. It is on 

 the deposits thrown up and conserved above 

 the high-water mark that the maritime plants 

 are especially found, and these form the first 

 zone, which may in the case of a low shore 

 line be of sand or shingle. Where there are 

 cliffs lashed at hi.gh tide by the sea there is 

 a single zone, the rocks and cliffs. But on a 

 low shore there are usually parallel with the 

 first sandy shore or shingle beach dunes of 

 reolian origin, whilst a third zone is constituted 

 by the salt marshes on the landward side of 

 the dunes, though these may not everywhere 

 be present, nor are dunes always developed on 

 a low shore. To leeward of the salt marshes 

 there may be a second line of dunes, and 

 then inland vegetation. There are normallv 

 three or four zones of vegetation on the sca- 

 coasl. 



Absence of Trees on the Sea-coast. -One 

 feature of most maritime tracts is the almost 

 universal absence of trees. This is due to the 

 regular occurrence of .sea breezes and land 

 breezes, which constantly subject the coast to 

 unusual wind force, so that trees are unable 

 to flourish except in a dwarfed state, and 

 generally have their branches blown land- 

 wards. The exposed nature of the sea-coast 



also, apart from the wind, contributes to the 

 absence of trees. Another reason is the char- 

 acter of the soil, which is saline, and usually 

 of coarse texture unsuited to tree growth. 



The fact that along most coasts there are 

 relics of ancient submerged forests does not 

 denote that the maritime t)order was formerlv 

 more suited to .such conditions, but is an 

 indication of the great amount of submer- 

 gence or sagging that has occurred. Such 

 forests were originally not only above the 

 sea-level but a good distance inland. The 

 maritime formations ;ire thus without any 

 native forests of their own. From this cause 

 there is generally a relative absence of humus 

 in the soil, except in the salt marshes where 

 semi-marine peat is formed. 



An exception must be made to the foregoing 

 general rule in the case of sheltered coves and 

 estuaries, as in Devonshire, Somerset, &c., 

 where trees grow down to the sea margin, 

 at any rate on rocky coasts. There are some 

 shrubs that are characteristic of the sea-coast, 

 such as Tamarisk, Sea Buckthorn, Coton- 

 easter, and Elder is in manv places common, 

 as also the Tea Pl.mt. 



Exposure of the Sea-coast. — Except upon 

 loftv hills and mountains no type of vegetation 

 is so much exposed as that of the sea-coast. 

 It is this factor which causes the vegetation 

 to have so distinctive a character, not only as 

 regards height and form, but also in regard 

 to its physiological adaptation to dry condi- 

 tions. One reason of this exposed character 

 is the relation of the sea to the land. The 

 maritime zones are constantly being exposed 

 to the land and sea breezes, which set up 

 regular air currents periodicall)". The general 

 absence of trees or of shrubs thus subjects the 

 ground vegetation to the influence of the wind 

 and the other factors. 



The winds which blow to the land bring 

 with them salt, which accumulates upon the 

 coastal vegetation, and for this reason the 

 maritime plants are halophytes, or plants 

 adapted to soil in which there is a large pro- 

 portion of chloride of sodiimi, as well as some 

 bromides and iodides. 



