230 ON BOTANICAL GEOGRAPHY. 



situated at the Cape of Good Hope, while another por- 

 tion of the same family grows in Van Dieman's Land. 

 Botanists have of late paid great attention to this subject ; 

 but the results of their researches can be considered only 

 as temporary, as it will ever be liable to change so long 

 as unknown plants remain to be investigated. 



Emily. Cannot you give us some idea of the result of 

 their researches ? 



Mrs. B. It has been calculated, for instance, that in al- 

 most all the botanical regions of the world one sixth of 

 the plants are monocotyledons ; and that, in regard to the 

 other two classes ; the number of dicotyledons increases 

 as you approach the equator, and that of the acotyledons, 

 on the contrary, as you draw nearer towards the pole. 

 This rule does not prevail in islands situated at a great 

 distance from any continent : in these the proportion of 

 monocotyledons is greater, and that of the dicotyledons 

 less, than is usually found in continental regions of the 

 same latitude. 



' Caroline. You do not mean to say that the same pro- 

 portion of monocotyledons exist in Europe as in Asia 

 in cold northern countries as in tropical climates ? To 

 judge from the views I have seen of India, the greater 

 part of the trees are of the family of Palms. 



Mrs. B. A few of such magnificent trees make a 

 great show in a landscape ; but reccollect that all our corn 

 and grasses are monocotyledons. The difference between 

 this class in England and in India consists, not in the 

 number, but in the size, of the plant. The vigorous veg- 

 etation of tropical climates produces monocotyledons of 

 stupendous dimensions, while the chilling temperature of 

 northern regions checks their growth ; and if we go be- 

 yond the gramineous family, it is but to produce lilies, 

 tulips, hyacinths, and other imperfectly-developed bul- 

 bous roots. It is only in the most southern parts of Eu- 

 rope that a few straggling palms denote the approach to 

 a more vigorous region of vegetation. 



Caroline. But tropical climates produce corn and 

 grasses as well as palm-trees. 



1509. What else often happens of the different general 1510. 

 Emily asks what is the result of the researches of botanists in this part of 

 the science What is the answer 1 1511. Where does this rule not 

 prevail 1 ? 1512. In objection to Mrs. B. what question does Caro- 

 line propose'? 1513. What is the reply 1 ? 1514. What is said of 

 the growth of the palm in Europe! 



