STATISTICS OF VEGETATION. 573 



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

 Brazil. 



14. Form of Succulent plants. Seen in the Mesembryacese of South Africa. 



1 5. Lily Form. This includes Liliaceje, Amaryllidaceae, and Iridacea. Mo- 

 difications of this form occur in warm and temperate climates. 



16. Forms of Lianas or Climbing-plants. These forms are chiefly tropical, 

 and are illustrated by Passion-flowers, Paullinias, Aristolochias, and Bauhmias. 



17. Pothos Form. This is a tropical form, and is illustrated by various spe- 

 cies of Aracece 



18. Orchid eous Form. This is seen in the splendid Epiphytes of warm cli- 

 mates. Terrestrial species chiefly occur in cold zones. 



19. The Moss Form. 



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

 Besides the forms of plants, it is found that the prevalent colours 

 sometimes give a character to the vegetation. White or pale-coloured 

 flowers are said to be more abundant in northern latitudes than in the 

 tropics, and in alpine situations they are of more frequent occurrence 

 than in the plains. The xanthic series of colours, Hinds states, is 

 abundant within the tropics in the autumn, on the plains over the 

 mountains. The flowers of the cyanic series, especially intense blues 

 and violets, delight in the clear skies of subtropical regions. Hinds 

 gives the following tabular view of the relative proportion of colours : 



Cyanic. Xanthic. White. 



Central America, 12 30 8 



Sandwich islands 12 31 7 



Alashka, 26 13 11 



California, 25 19 6 



New Guinea, 12 23 15 



Hong-Kong 13 27 10 



Geyer says, that vivid colours mark the basaltic plains of Upper 

 Oregon; blue and purple, eastward; scarlet with golden-yellow, west- 

 ward ; glaucous green reigns in the herbage over the plains ; deep 

 saturated green in the vallies. 



1151. statistics of Vegetation. The number of known vegetable 

 families differs in different latitudes. In examining the distribution 

 of the great classes of the Vegetable Kingdom, it will be found that 

 certain relative numerical proportions have been ascertained. It is 

 not easy to estimate the proportion which Cryptogamous bear to Pha- 

 nerogamous plants. From data already given, it may be estimated 

 that the proportion for the whole world is as 1 to 7. This proportion 

 varies in different regions ; the Cryptogamous plants increasing in 

 cheir proportion in the northern parts of the temperate zone. Ferns 

 are to known Phanerogamous plants as 1 to 20. This proportion is 

 least in the middle of the temperate zone, and becomes larger towards 

 the equator, and towards the poles. Ferns, however, attain their ab- 

 solute maximum at the equator, and their absolute minimum in the 

 arctic zone. At North Cape, there are only four species of Ferns 

 found, and yet their proportion to Phanerogamia is 1 to 7 there ; and 



