46 BOTANY. 



9. Coniferous Form. The Abietin» are characteristic of northern regions, 

 and Cupressineas of southern. 



10. The Protea, Epacris, and Erica Forms. These forms supply the 

 place of Coniferae in the southern hemisphere ; the Protea and Epacris 

 forms occurring in Australasia, and the Erica form at the cape of Good 

 Hope. 



11. Myrtle Form. Some of these, such as Melaleuca and Eucalyptus, 

 characterize New Holland Scenery ; others, as Guavas, are tropical. 



12. Forms of Dicotyledonous Trees. Some, with broad and tender 

 leaves, as Birch, Alder, Poplar, Oak, Lime, Elm, Beech, and Horse-chestnut, 

 giving a character to the physiognomy of the colder half of temperate climates ; 

 while others, with thick, leathery, and showy leaves, as Olives and Laurels, 

 are characteristic of warmer climates ; and a third division, with large, 

 beautiful leaves, Cecropia, Artocarpus, and Astraprea, abound in the hottest 

 climates. 



13. Cactus Form. This form is developed chiefly in America, especially 

 in Brazil. 



14. Form of Succulent Plants. Seen in the ]\Iesembryace8e of South 

 Africa. 



15. Lily Form. This includes Liliaceee, Amaryllidacca?, and Iridaceae. 

 Modifications of this form occur in warm and temperate climates. 



16. Forms of Lianas, or Climhing-Plants. These forms are chiefly 

 tropical, and are illustrated by Passion-flowers, Paullinias, Aristolochias, and 

 Bauhinias. 



17. Pathos Form. This is a tropical form, and is illustrated by various 

 species of Araceae. 



18. Orchideous Form. This is seen in the splendid Epiphytes of warm 

 climates. Terrestrial species chiefly occur in cold zones. 



19. The Moss Form. 



20. The Lichen Form. Both these forms characterize cold regions 

 chiefly. 



In treating of the geographical arrangement of plants, we may consider 

 them under two points of vicAV ; first, as respects the horizontal or latitude 

 arrangement; and second, in respect to the vertical range. The mean tem- 

 perature of the earth diminishes as we travel from the equator towards 

 either pole, as also in ascending to the top of a high mountain from its 

 base ; so that there is a certain parallelism between the horizontal range of 

 mean temperature and the vertical. The same is the case in plants, as we 

 shall find that the same mean temperature, Avhether we attain this by a hori- 

 zontal or by a vertical progression, is characterized by the same vegetable 

 features. 



Considering, in the first place, the horizontal range of vegetation, we find 

 the following to be the divisions of Meyen, the latest authority on the 

 subject : — 



46 



