270 Transactions. — Botany. 



period through the agency of man, direct or indirect, or whether it is that 

 in addition to possessing great flexibility of character and consequent power 

 of adapting themselves to varied conditions, they have also been able to 

 spread widely by natural means of migration, it is now for the most part 

 impossible to say — probably both causes have operated. Their wide ranges, 

 however, make it difficult to state their distribution with exactness, but the 

 following will be found to be a sufficiently close approximation. 280 are 

 natives of Europe, many of them also ranging into temperate Asia and 

 North America, and some into North Africa, but for our purpose it is not 

 important to specify these. 10 species, not European, are from the eastern 

 portion of North America, and 4 are from the western side of the same 

 continent. This will make a total of 294 species introduced from the north 

 temperate zone. From Australia, notwithstanding its nearness to us, we 

 have only received 10 ; from Chili and the cool portions of South America, 

 9 ; from the Cape of Good Hope, 21. The number naturalized from the 

 south temperate zone is thus only 40. Finally, there are 58 species from 

 the subtropical and tropical portions of both hemispheres, most having a 

 very wide distribution. 



"With respect to the habit and duration of the species, only 31 are trees 

 or shrubs, the remaining 356 being herbaceous. Of this latter number 176 

 are annual, 28 biennial, 152 perennial. The large proportion of annual 

 species is noteworthy, as in the indigenous flora nearly all the herbaceous 

 plants are of perennial growth. 



If it is endeavoured to divide the species into groups according to the 

 nature of then- habitats, it will be found that nearly two-thirds fall, in about 

 equal numbers, into three classes : first, weeds of cultivated lands and 

 gardens ; second, inhabitants of meadows or fields ; third, plants of road- 

 sides or waste places. Of the remaining third a considerable proportion 

 are escapes from gardens, or other plants whose position it is difficult to 

 define at present, and which occupy very various stations : littoral, paludal, 

 sylvestral, etc. 



Finally, we find that the species belong to 233 genera, arranged in 60 

 orders. The orders best represented are, — Graminea, with 60 species, 

 Composites 51, Leguminosce 35, Crucifera 20, Caryophyllea 15, Rosacea 14. 

 Of the genera no less than 182 are without indigenous representatives 

 in this country, and 16 of the orders are in the same position. The large 

 number of genera into which the species are distributed shows that our 

 naturalized flora is of a very diversified character ; and the fact that most 

 of the genera have no indigenous species, proves that naturalized plants, to 

 succeed in any country, need not have any close affinity with the pre-exist- 

 ing inhabitants. 



