S42 Observations on Humboldt's Wo7-ks 



geography of plants, have hitherto neglected the geographical 

 distribution of families. If he hereby means only the general 

 distribution, upon the whole surface of the earth, we must agree 

 with him; but, concerning the relative proportion of the families 

 of plants in particular countries, Dr. Wahlenberg, in his three 

 principal works*, has presented us with much valuable in- 

 formation. 



According to my conviction, there are too few materials at 

 present, to enable us to establish the laws of this distribution 

 with accuracy, certainty and perfection. Since, however, the 

 subject is of so great interest, every attempt to fix them even 

 provisionally, certainly deserves the warmest support; but here- 

 in we must proceed with the greatest attention and caution, I 

 propose to go through the chief points, which in my opinion 

 should be taken into consideration, and, with the permission of 

 M. Humboldt, notice at the same time, how far they have been 

 observed by him. 



In the present state of the science there are two methods, by 

 which the laws of distribution for different geographical lati- 

 tudes, or to speak more precisely, different climates, may be 

 investigated. We should either divide the surface of the earth 

 into certain zones, ascertain which of the known plants are 

 found in each zone, and then compare the different zones with 

 each other ; or we should first take some Floras of countries in 

 different climates, compare the plants which are found in those 

 countries, and draw conclusions from these with respect to the 

 distribution of plants in general. Of these two methods the 

 Author has chosen the last ; we do indeed find inscribed [upon 

 the heads of the table (No. 1., p. xviii.) Equatorial Zone, 

 Tempekate Zone, and Polar Zone, but in the calculations 

 prefixed to this table, he remarks that the computed distribution 

 of the equatorial plants is derived only from those found by 

 Humboldt and Bonplandtf, and the distribution in the polar 



* Flora Lapponica. Tentamen de climate et vegetatioue Helvetiae Sep- 

 tcntrionalis.— Hora Carpathorum. 

 t In fact, aa we shall sec presently, only from a part of tlie same. 



