THE INFLUENCE OF GEOLOGY ON HORTICULTURE. 



397 



yard manure, the ploughing in of green crops, and sheep folding. 

 Superphosphate is a good form of phosphatic manure ; potash is generally 

 needed. Salt is generally beneficial as an addition to manures on 

 calcareous rocks, especially for plants of the cabbage tribe. The lighter 

 calcareous soils are notoriously weedy ; fumitory (Fumaria officinalis), 

 dove's foot and crane's bill are characteristic weeds. Sainfoin and lucerne 

 flourish and provide abundant and valuable fodder even on the driest 

 chalk soils. 



The natural flora of the calcareous soils includes the beech, yew, 

 wild cherry, juniper, box, mealy guelder rose (Viburnum Lantana), 

 beam tree (Pyrus Aria), dogwood (Cornus sanguinea), and traveller's 

 joy (Clematis vitalba). It is rich in flowering plants, including the 

 horse-shoe vetch (Hippocrepis comosa), bird's foot trefoil (Lotus 

 corniculatus), kidney vetch (Anthyllis Vulneraria), milkwort (Polygala 

 sp.), bladder campion (Silene inflata), burnet (Poterium Sanguisorba), 

 wild parsnip (Pastinaca sativa), sheep's scabious (Scabiosa Columbaria), 

 common succory or chicory (Cichorium Intybus), and viper's bugloss 

 (Echium vulgare), marjoram (Origanum vulgare), which are 

 characteristic of the pastures and waste places on chalk and limestone. 

 Among the grasses, the downy and yellow oat grasses (Avena pubesccns 

 and A. flavescens), upright brome (Bromus erectus), and heath false 

 brome (Br achy podium pmnatum) are common. 



Plants characteristic of Loams. — Of plants indicating a good 

 fertile soil may be mentioned chickweed (Stellaria media), groundsel 

 (Senecio vulgaris), fat hen (Chenopodium album), sow thistle (Sonchus 

 oleraceus), goose grass (Galium Aparine), speedwells (Veronica agrestis, 

 &c), pimpernel (Anagallis arvensis), henbit (Lamium amplexicaule) , 

 wild poppy (Papaver Bhoeas), the small spurge (Euphorbia Peplus), 

 strong-growing stinging nettles, tall thistles, and sturdy hedgerow timber. 



Plants of Peaty Soils. — Conifers, heather, Sphagnum, sheep's sorrel, 

 louse-wort, sedges, rushes, and sundew are characteristic of peaty soils. 

 The first steps towards improving these soils are to drain them and then 

 to apply lime. 



Plants tolerant of Salt. — Mangels, asparagus, cabbage, seakale, 

 common thrift or sea pink, and the sea aster tolerate salt soils, but 

 thrive well in ordinary soil. The orache, beet, sea lavender, sea heath, 

 seakale, and samphire are found in salt marshes. 



Plants intolerant of Salt, even in small proportions, include the rose, 

 orchid and heath families, and stinging nettle. 



Plants that generally grow on Land that requires Drainage include 

 coltsfoot, Eguisetum, cuckoo flower, water mint, sedges and rushes. 



The geologist classifies rocks into 



I. Igneous — such as granite and trap. 



II. Sedimentary or Stratified— such as clay, shale, sandstone, lime- 

 stone, and chalk, deposited in the sea or in fresh water. 

 III. Terrestrial — due to the growth of vegetation on the land, such as 

 coal and peat. 



The Stratified rocks are divided into three' periods, based on the 

 animals and plants found as fossils in them ; thus — The Primary, or 



