Grasses like _Bromus arvensis_ indicate the existence of clay in the soil. While the following are indicative of sand, _Aira caryophyllea._ _A. præcox._ _A. canescens._ _Festuca ovina._ _Bromus sterilis._ And only if the sandy soil is moist and of better quality, owing to a certain proportion of humus, the following, _Anthoxanthum odoratum._ _Agrostis alba._ _Dactylis glomerata._ _Arrhenatherum avenaceum._ _Avena pubescens._ _Poa pratensis._ That the soil contains considerable quantities of common salt--sodium chloride--may be inferred if the following grasses occur, _Psamma arenaria._ _Elymus arenarius._ _Hordeum maritimum._ _Agropyrum junceum_, &c. The existence of much humus is indicated by such shade grasses as _Melica uniflora._ _M. nutans._ _Milium effusum._ _Bromus giganteus._ _B. asper._ _Brachypodium sylvaticum._ Whereas soils known as “sour,” though containing much vegetable remains, may be suspected if the following grasses abound on them, _Aira cæspitosa._ _Nardus stricta._ _Alopecurus geniculatus._ _Molinia cærulea_; especially if sedges and rushes coexist with them. When cuttings are made in forests, such grasses as the following are very apt to appear, and may do harm to young plants, _Festuca ovina_ and varieties. _Agrostis alba._ _Holcus mollis._ _Aira flexuosa_, &c. The grasses more especially indicative of particular classes of forest-soils are chiefly the wood-species (see p. 28), and need not be further specified. In gaps, borders, and copses--half-shade--we find several common grasses--e.g. _Anthoxanthum odoratum._ _Agrostis alba._ _Aira flexuosa._ _Holcus lanatus._ _Arrhenatherum avenaceum._ _Triodia decumbens._ _Dactylis glomerata._ _Festuca rubra._ _Brachypodium pinnatum._ _Hordeum sylvaticum._ Whereas _Poa nemoralis_, _Festuca sylvatica_, _Agropyrum caninum_, _Melica_, _Milium_, _Bromus asper_, _B. giganteus_, _Brachypodium sylvaticum_, are more likely to be met with in the deep shade inside the forest. On the other hand there are vagabond grasses which seem to show no signs of preference for one soil over another--e.g. _Poa annua_--though in some cases these _ruderal_ plants indicate the presence of rotting substances, on ash-heaps and rubbish of various kinds. With reference to the above, however, the student must not forget that very complex relations are concerned in changes of soil, shade, moisture, elevation, &c. and that although experienced observers can draw conclusions of some value from the presence of _numerous species and individuals_ on a given soil, no one must conclude too readily that a soil is so and so, from observing solely that a particular kind of grass will grow there.