272 



SCIENCE OF AGRICULTURE. 



Part II. 



4| ; in New Holland the three grand divisions of plants, beginning with the acotyledoneae, 

 are nearly as 1 , 2i, and 7|. 



1744. Dicotyledoneee. In the whole globe, the monocotyledoneae are estimated, by 

 R. Brown, from Persoon's Synopsis, [Gen. Rem. ontheBot. of Terr. Aust. 1814.) to be 

 to the dicotyledonesc as 2 to 1 1 ; or with the addition of imdescribed plants, as 2 to 9. 

 From the equator to 30 of north latitude, they are as 1 to 5. In the higher latitudes a 

 gradual diminution of dicotyledoneae takes place, until in about 60 nortli latitude and 

 50 south latitude they scarcely equal half their intertropical proportions. The ferns in 

 the temperate regions are to the whole number of species as 1,2, and 5 ; that is, in the 

 polar regions as I, in the temperate countries as 2, and in the intertropical regions as 5. 

 Ill France, ferns form ^^ part of the phanerogamous plants ; in Germany ^'g ; in Lap- 

 land Jg. 



1745. The natural orders of perfect or phanerogamous plants are variously distributed 

 in different countries. The following Table gives a general view of the relative propor- 

 tions of several natural orders of perfect plants in France, Germany, and Lapland. 



1746. The most universal plants are the agamous 

 families. Their germs are the only ones which nature 

 developes spontaneously in all climates. The poly- 

 trychum commune (Jig. 244.) grows in all latitudes; 

 in Europe and under the equator ; on high moun- 

 tains and on a level with the sea ; in short, wherever 

 there is shade and humidity. No phanerogamous 

 plants have organs sufficiently flexible to accommodate 

 themselves in this manner to every zone. The alsine 

 media, fragaria vesca, and solanum nigrum, have been 

 supposed to enjoy this advantage ; but all that can be 

 said is, that these plants are very much spread, like the 

 people of the race of Caucasus, in the northern part of 

 the ancient continent. (Humboldt.) 



Sect. VI. Economical Distribution of Vegetables. 



1747. The plants chiefly employed in human economy differ iii different climates and 

 countries ; but some, as the cereal grasses, are in universal use ; and others, as the banana 

 and plantain, only in the countries which produce them. 



