the Vegetation of a Country. 439 



It is not always correct, seeing that the Cyperacese and 

 Graminese, which constitute the greater portion of the ]\Ionoco- 

 tyledones in most countries, and the Orchidere in some warm 

 and moist regions, are precisely the families of the exact number 

 of which we know least. There are many Floras, even of 

 European countries, in which the number of Cyperacese is very 

 incomplete. As a general rule, the more completely the Flora 

 of a district or province is known, the more does the proportion 

 of Monocoiyledoncs increase ; but this is probably not the case 

 with the Floras of very extensive countries, from another cause 

 to -which I shall refer hereafter, a cause which has escaped the 

 attention of authors who are generally very judicious. 



The comparison of the numbers must not be made between 

 countries of unequal extent, because the average area* of the 

 species of Monocotyledones is much larger, at least in our tem- 

 perate and northern regions, than the average area of the Dico- 

 tyledones. In the Flora of a pi'ovince we meet with the greater 

 part of the Graminea?, Cyperacea^, and Juncacese which exist in 

 an extensive region around this province. The more extended 

 the space under consideration, the more are local species added 

 to the Flora, and these are most frequently Dicotyledones. The 

 following are a few examples in confirmation of this : — 



The Flora of the department of Maine-et-Loire, by M. 

 Guepin (ed. 3), shows the proportion of the Monocotyledones to 

 the Dicotyledones to be 1 : 3*2. The Flora of the same de- 

 partment, with several others of the centre of France, by M. 

 Boreau, gives the proportion 1 : 35 ; and that of the whole of 

 France, according to the Botanicon of M. Duby, = l : 4'3. To 

 give these fractions in a more complete and logical form, I will 

 say that in the department of Maine-et-Loire the ^Nlouocoty- 

 ledones constitute 23* 7 per cent, of the phanerogamous plants, 

 in the central departments of France (including the preceding) 

 22*2 per cent., and in the whole of France IS'Sf. 



If we could extend our observations to the whole of Europe, 



* The area, in botanical geography, is the surface occupied by a species, 

 a genus, or a famih'. 



t The cultivated species are excluded from these numbers. We find 

 the same differences in taking separate portions and the whole of the 

 German Floras, between the Adriatic and the Baltic. Thus, in Dalmatia, 

 the proportion is I : 3"5, according to M. Yisiani's Flora (vol. iii. p. 390) ; 

 in Lower Austria, 1 : 3*7 (Neik. Fl. Wien. p. xxxi) ; in Wurtemberg, 

 1:31 (Schiibler and Martens, p. xv); in the Kingdom of Saxonv, 1 : 3o 

 (Reichb. Fl. Sax. ed. 1844); in Silesia, 1 : 3-2 (Wimm. and Grab. Fl. 2. 

 p. 95); in the province of Pnissia, 1 ; 3'2 (E. Mey. Fl.). For the whole 

 of Germany the proportion, according to Fiirm'ohr (Fl. de Ratisb.p. xxxi), 

 is 1 : 3'7, or including the Austrian possessions on the shores of the 

 Adriatic (Koch, Syn. ed. 1. p. Ix), 1 : 38. 



