THE 



NATUEAL HISTOEY OF PLANTS. 



INTRODUCTION. 



Sources of a History of Plants. — The Language of Botanists. 



SOUECES OF A HISTORY OF PLANTS. 



From the sixteenth to the latter part of the eighteenth century, " Historia plant- 

 arum" was the customary title for botanical works. Most of the scholars of that 

 time took as their authorities and models the writings of Theophrastus, the cele- 

 brated pupil of Aristotle, together with the thirty-seven books constituting Pliny's 

 "Historia naturalis". Thus it came about that the titles of the new books were 

 similar to those of Theophrastus and Pliny. However, all these books are anything 

 but histories of plants, if in the idea of a history we include an account of the 

 changes which occur within the limits of space and time. In reality the bulky 

 folios of Clusius, Bauhin, and Haller, the title-pages of which bear the inscription 

 "Historia plantarum", contain descriptions merely of the external characters of 

 plants, accompanied by only sparing details of the situations in which these plants 

 had been found growing wild. Works of this kind, dealing with limited areas of 

 country, were later on distinguished by the name of Floras. By this name they 

 are still known. 



Although the authors of the Flora had no such purpose in view, their works 

 furnished the starting-point for a real history of the vegetable world. A com- 

 parison of the Floras of neighbouring regions shows that certain plants inhabit 

 a greater, others a lesser area; that the boundaries of the species confined to a 

 distinct district coincide with territories inhabited by various races of mankind; 

 that the boundaries of this and that species coincide and stand in relation to 

 various climatic and other conditions. 



All plants have the power of propagating themselves. They send their ofispring 

 forth as colonists towards all points of the compass, and endeavour in this way to 

 enlarge their areas of distribution. Suppose that a species hitherto subsisting in 

 localities where there are seven months of snow and five months of vegetation in 

 the year multiplies, and that its descendants are scattered in all directions, what 

 would happen if any of these emissaries reached places where frost and snow 



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