244 



HINTS AND NOTES 



Soil and Upland Plants. — Hills, as has been 

 explained, aro largely the result, apart from 

 cenuding agencies and river development, of 

 uplifts or rearrangements of the crust, thus 

 causing a diversity of rocks to be exposed at 

 the surface. Many types of rock may thus 

 outcrop within a short distance, and the plants 

 of a single hill or mountain may thus be of 

 very diverse types. As explained also else- 

 where, the older sandy or siliceous types are 

 mainlv developed in the west and north, 

 though modern arenaceous rocks occur in the 

 east and south also. Central England, as a 

 whole devoid of hills, is largely made up of 

 clays, loams, marls, and eastward there are 

 calcareous rocks and chalk, with peaty condi- 

 tions in the lowlands. 



The Pennine Axis, and other regions in the 

 west, and Lake district are made up of lime- 

 stone. 



The plants that are described are found upon 

 all these types of soil. Weld, Rock Rose, 

 Hairj' Violet, Kidney Vetch, Sainfoin, Drop- 

 wort, .Salad Burnet, Wild Thyme, Clary, Box, 

 Musk Orchid are found largely on limestone 

 or chalk, though sandy soil also suits some of 

 these. .-X sandy soil suits Marsh Mallow, 

 Rest Harrow, Hare's Foot Trefoil, Field 

 Scabious, Cotton Thistle, Sheep's Sorrel, 

 Sheep's Fescue. But Hairy Violet may be 

 found on a sandy or a humus soil. Humus 

 also suits the Gentians and Fragrant Orchid. 

 Touch-me-not requires peat like the last to 

 some e.xtent. Silky Mountain Vetch requires 

 a rocky stony soil. 



Method of Survey. — The reason for the sep- 

 aration of hills, &c. , from other types of habitat 

 being mainly one of altitude, the method of 

 survey in this case must be, in order to obtain 

 .satisfactory results, carried out by surveving 

 zones of altitude. That is to say, a region 

 from i-ioo ft., and so on upward, should be 

 marked off by aid of an aneroid, or oro- 

 graphic maps, or contours on an ordnance 

 map. The altitudes of plants found between 

 such zones will then be obtained, and it will 

 be possible to determine by such data the 

 exact range upward or downward of each 

 species. 



The mode of survey of each piece of ground 

 as an area should be done in the case of the 

 types so far described on those lines, whilst 

 bog and heath or moor may be surveyed, as 

 also any aquatic vegetation, on the lines of the 

 method of survey described elsewhere. There 

 may be pasture (usually predominant), or corn- 

 lield, or wood, or roadside and hedges, which 

 should be studied as already suggested. 



Other special points to be noticed, and of 

 which data should be kept, are the eflect of 

 the wind force, the temperature, and the length 

 of sunlight, rainfall, &c. The aspect and 

 slope, the latter given in angles, and the char- 

 acter of the soil, are all factors that should be 

 noted and put down. The dr}- or wet character 

 of the soil is important, and advanced students 

 may estimate the water content. .-Vny points 

 that may be noted as to the influence of one 

 species upon another are also of the highest 

 importance. 



SECTION VIII 



LAKES, RIVERS, STREAMS, DITCHES, 

 AND WET PLACES 



Terrestrial and Aquatic Vegetation. — Water 

 has a more uniform temperature than the soil, 

 and thus aquatic vegetation is more or less 

 constant, for the chief zones of latitude. But 

 adaptation to an aquatic life necessarily in- 

 volves particular habits, &c. Many water 

 plants are found all over the world. This may 

 be due in part to the migration of water-fowl. 



Aquatic plants form open associations, but 

 are not in this case so subject to the encroach- 

 ment of other plants, except riparial types; 

 and it is here that the invasional factor comes 

 into play. .Some plants in fact are amphibious, 

 and can live in water and on land. 



Water plants derive their air through the 

 water, so that they have wide air-sp;ices. The 

 leaves are thin and much divided, because the 

 light coming through the water is aln-.uly 

 diffused or broken. 



Some aquatic plants float freely upon the 

 surface, as Duckweed; others are rooted in 

 the mud, as Water Lily, and raise their leaves 

 above water; whilst others are submerged. 

 There are those that grow half in and half out 

 of water, or at the margin. Thus the vegeta- 

 tion of the water exhibits every transition to 

 that of the land. 



Hydrophytes or True Aquatic Plants. — .Aquatic 



