388 PROTECTION AGAINST PLANTS. 



On sandy soils we find chiefly ling (Calluna vulgaris, Sal.) 

 and heather (Erica), broom (Cytisus scopfirius, Link.), lyme- 

 grass (Elymus arenarius, L.), maram-grass (Psamma arenaria, 

 Beauv.), sand-sedge (Carex arenaria, L.) ; Festuca glauca, 

 Schrad. ; Panicum glabrum, Gaud. ; etc. 



On clay soils: coltsfoot (Tassilago Farfara, L.), wound- 

 wort (Stacliys palustris, L.), marestail (Equisetum) , cotton- 

 grass (Eriophorum), rushes (Juncus). 



On loam, on account of its favourable nature, very numerous 

 weeds abound, such as all good meadow-grasses, bindweed 

 (Convolvulus), Veronica^ etc. 



Calcicolous weeds are Viburnum Lantana, L. (way faringtree ; 

 rock-rose (Helianthemum vulyare, Gaertn.) ; Stacliys germanica, 

 L. ; Eubus saxatilis, L. ; many Papilionacece, and of grasses, 

 Melica and Sesleria. 



On rich humus soil: raspberry (Rubus Idaeus, L.), balsam 

 (Impatiens Noli-me-tangere, L.), hemp-nettle (Galeopsis Te- 

 trahit, L.), black night-shade (Solanum nigrum, L.), etc. 



On peats: -we find mint (Mentha pulustris, L., etc.); bog 

 myrtle (Myrica Gale, L.) ; Vaccinium idiginosum, L. ; Carex, 

 Eriophorum, Juncus, Scirpus, lousewort (Pedicularis), dock 

 (Rumex), loosestrife (Ly thrum Salicaria, L.), peat-moss 

 (Sphagnum, sp.), etc. 



On saline soils : sea milk- wort (Glauxmaritima, L., Plantago 

 maritima, L.), samphire (Crithmum maritimum, L.), marsh- 

 samphire (Salicornia herbacea, L.), salt- wort (Salsola Kali, 

 L.), Armeria vulgaris, Willd. ; sea-lavender (Statice), sea-holly 

 (Eryngium maritimum, L.), maram-grass, etc. 



e. Mineral Substances in Ashes of Weeds. 



The mineral character of the soil on which plants will thrive 

 cannot be decided by the quantity of any substance such as 

 silica, calcium carbonate, or sodium chloride, which may be 

 found in their ashes. Different parts of the same plant 

 also contain different proportions of chemical substances. 

 Thus, there is much silica in the stem of grasses, and more 

 phosphates and potash in their seeds. 



The physical nature of the soil, i.e., its degree of moisture, 



