892 PLANT COMMUNITIES AND FLORAS. 



will therefore only make a few observations on the subject, and draw attention to 

 the most striking cases of plant-communities. 



The gi-eatest interest naturally attaches to forests which impress the observer 

 by their size, and it is easy to understand why these have always been chosen for 

 the most thorough investigation and description. As regards the species which are 

 either the only constituents of the commimity, or at any rate its ruling members, 

 we must first distinguish forests of deciduous Conifers and those of evergreen 

 Conifers. A Larch forest (see fig. 354, p. 483) may be taken as an example of the 

 former. Of the evergreen variety there is an extremely large number, owing to the 

 fact that most true Conifers grow in dense forests. A forest of Spruce Firs is 

 represented on p. 415, vol. i., a forest of Silver Firs on p. 717, vol. i., of Scotch Pines 

 on p. 723, vol. ii., and of AroUa Pines on p. 724, vol. ii. Forests composed of 

 Angiosperms are likewise differentiated into deciduous and evergreen. Amongst 

 deciduous forests of this kind the Beech-woods (see p. 761), Birch-woods (see p. 721, 

 vol. i.), and Oak forests (see vol. i. p. 716, fig. 173) of the North Temperate Zone 

 are especially noticeable on account of the characteristic aspect exhibited in 

 each case. Angiospermous evergreen forests manifest their greatest variety in 

 tropical and sub-tropical regions. To the Tropics belong also a number of other 

 special kinds of forest, such as those composed of Euphorbias, Casuarinas, Bamboos 

 (see vol. i. p. 713, fig. 172), of Mangroves (see vol. i. p. 605, fig. 143, and p. 759, 

 fig. 187), and of Palms (see vol. i. Plate VIII. opposite p. 712), respectively. Drawings 

 from nature in the Tropics representing Bamboos and Mangroves are also given in 

 figs. 481 and 482. 



Scrubs, wliich are, so to speak, repetitions of woods or forests in little, may be 

 similarly divided into groups. We distinguish between those in which the shrubs 

 and semi-shrubs, which are predominant or in exclusive possession, are leafless and 

 those where the shrubs are provided with foliage. Amongst the social plants of the 

 first group switch-plants and certain cactiform plants play a prominent part (see 

 vol. i. p. 331, fig. 80, and Plate IV. p. 446). The social plants of the second group are 

 either evergi-een or deciduoiis. The former are furnished with acicular or squami- 

 form leaves which are appressed to the branches (shrubby Conifers and Heaths), or 

 else are clothed with flat, expanded leaves. The case of Alpine Roses (see Plate X.) 

 will serve as an example of the second variety. Amongst deciduous shrubs and semi- 

 shrubs which grow sociably and form extensive scrubs we may mention Tamarisks, 

 Spiraeas, Eoses, Dwarf- Almonds, Dwarf-Birches, Dwarf- Willows, Proteaceas, Labiatse, 

 Broom, and Mimosas. 



As regards plains we must first distinguish those where the predominating 

 perennial plants have no foliage-leaves, but are furnished instead with green, fusi- 

 form shoots and branches of a foliaceous nature (e.g. Salicamia). Of leafy plants 

 which occur as predominant members of plains we may mention Umbellifers, 

 Thistles (see vol. i. p. 436, fig. 115), Agaves and Pine-apples (see vol. i. p. 657, 

 fig. 153), and the Asphodel (see fig. 413, p. 729), as the most striking examples. 

 The rest of the social sufl'rutices may be placed in three groups. The species 



