COLONIZING SPECIES. 569 
than in herbaceous Papilionaces, Labiatex, and some other orders 
not endowed with any specially evident facilities for dispersion. 
I cannot reckon above seventy species which have in recent 
times naturalized themselves in countries distant from their own. 
I must, however, acknowledge that the following lists may be 
very imperfect. It would require much more time than I have 
been able to bestow to glean the necessary data from the multi- 
tudinous publications in which they are noted, and still more to 
form a correct idea of the value of these data. Local botanists, 
and especially travelling colleetors, rarely distinguish between a 
single apparently wild individual which may have been planted, 
or may have once or twice sprung up without further propagation 
and a well-established weed. These lists, however, such as they 
are, may be sufficient to found some considerations on the specific 
qualifications best suited for successful colonization, and which 
may be taken as supplementary to the elaborate treatment of the 
general subject in the second volume of A. De Candolle's * Géogra- 
phie Botanique, more especially to the head of * Naturalisation 
à grande distance," p. 709. 
We may, in the first place, distinguish escapes from cultivation 
and weeds of cultivation—the former being plants specially intro- 
duced by man for ornament or use, and which have spontaneously 
spread from the spots where he had planted them ; the weeds of 
cultivation including all those which man had unintentionally 
transported, either mixed with the cultivated seeds or attached to 
goods transmitted, or with ballast, or other means connected with 
transmarine or terrestrial overland traffic. 
Table 18. Composite escapes from Cultivation. 
Species. Where established. Qualifications. 
a. of American origin. 
Aster saliznds 5 Seno Marshes and wet places in | Pappus. Marsh-plant. 
many parts of Europe. 
Europe, chiefly Germany, 
banks of streams. 
Aster Novi Belgii and a Pappus; persistent root. 
few others. 
Solidago canadensis......... 
Zinnia, two or three species 
or varieties. 
Europe and some other AS 3 
temperate countries. 
Atlantic islands, tropical 
and subtropical Africa 
and Asia. 
Abundance of seed ; ready 
germination? 
