62 INVASION 



to contrast with introduced, and employed the word aborigi- 

 nal to denote peculiar plants. The latter, as he has showni 

 are due to barriers, and are of primary importance for the 

 limitation of floral regions, of which he distinguished twenty. 

 With respect to distribution, he distinguished endemic genera 

 and families, composed of species growing in a single 

 country, and sporadic genera, which are distributed over the 

 entire world. Schouw (1823:505) extended the use of peculiar 

 species in the recognition of regions, and laid down the fol- 

 lowing rules: '=Um ein pflanzengeographisches Reich zu 

 bilden verlange ich von einem Theile der Erdoberflache ; 1. 

 dass wenigstens die Halfte der bekannten Arten diesem 

 Brdtheile eigenthtimlich gehOre ; 2. dass wenigstens i der 

 Gattungen entweder vOllig eigenthtimlich sey oder doch 

 wenigstens in dem Erdtheile ein so entschiedenes Maximum 

 habe, dass die in anderen Erdtheilen vorkommenden Arten 

 nur als Repraseatanten zu bebrachten sind. 3. Dass einzelne 

 Pflanzenfamilien gleichfalls entweder diesem Erdtheile 

 eigenthiimlich seyen, oder wenigstens ein entschiedenes 

 Maximum dort haben. Doch diirfte man wohl, selbst wo das 

 letztere Requisit fehlt, den Erdtheil als ein besonderes 

 Reich ansehen, wenn die Verschiedenheiten der Gattungen 

 bedeutend sind." Fend (1833: J9) proposed to replace the 

 word sporadic, because of its use in migration, loj polydemic, 

 and suggested the term pandemic for truly cosmopolitan 

 species. Meyen (J836: J60), while he recognized the value of 

 Schouw's statistical method, emphasized more particularly 

 the importance of physiognomy, i. e. mass, habit and dis- 

 tribution, in determining the divisions of vegetation, a 

 method already employed by Treviranos ( 1802 : 85), but with- 

 out success on account of the rudimentary development of 

 the subject. 



A. DeCandoIIe (1855:476) rejected the terms endemic and 

 sporadic for reasons which do not seem very valid. He 

 brought together in the chapters on the delimitation and 

 area of species an enormous mass of facts, many of which 

 have a direct bearing upon endemism. Darwin (1859 ; 66) con- 

 sidered at some length the proportion of endemic species in 



