122 DISSEMINATION OF SEEDS. 



alone or surrounded by the pericarp, fall to the ground. 

 Here, under peculiar and favorable circumstances, they 

 germinate, continue to grow, and develop into new indi- 

 viduals possessing the important characteristics of the 

 plants which produced them. 



So long as scientific men believed that "the several 

 species of plants were special creations formed to live in 

 those countries in which now found," their habitat and 

 mode of perpetuation called for no discussion ; they were 

 facts requiring no explanation. At the present time, 

 however, with the advance that has been made in the 

 study of plants, we find ourselves obliged to inquire what 

 provision has been made for the dissemination of the 

 seed ; how it has come to pass that the same plants are 

 found as members of the floras of countries widely sepa- 

 rated ; how that natives of the mountain-tops of certain 

 lands are found, apparently growing wild, in polar regions 

 far away ; how that the fossil plants of some lands are 

 the living plants of others ; how that the plants of tropi- 

 cal regions are sometimes found flourishing on distant 

 shores. 



The answering of these questions is a work by no 

 means easy since so many elements enter into the consid- 

 eration, each one in itself important and each requiring 

 a large amount of careful consideration. To understand 

 fully all the means provided by nature for bringing about 

 these results, we need a complete knowledge of the flora 

 of the whole world, of the natural classification of living 

 plants, of the forms of plant-life existing thousands of 

 years ago but now extinct, of the known effect of changes 

 in climate upon living organisms, of the changes that 

 have been made in the relative position of land and water 

 upon our earth, of the modern theory of the "origin and 

 development of species." 



