600 THE SUBDIVISIONS OF THE VEGETABLE KINGDOM. 



changes, of the older, less fit forms some are extinguished, whilst young, new 

 forms step into their places. • Thus we see also that the convei'sion of Mosses 

 into Ferns, of Ferns into Conifers, and of Grasses into Pinks, &c., as assumed 

 by the theory of progressive transformation, would be a positive disadvantage 

 to plants as a community, and that its tendency would be in the direction of 

 anything but real progress. 



It is important to recognize the fact that in the production of new forms by 

 crossing, it is not especially such forms as are constituted to resist an anticipated 

 change of climate that are produced. Of the forms which arise, some are fitted 

 for a more inhospitable, others for a milder climate; but it cannot be said of any 

 that they possess an assured future. Such only are able to maintain, propagate, 

 and establish themselves, as are from their internal organization and external form 

 in harmony with the prevailing climatic conditions of the moment. Those so 

 constituted that they are unable to thrive under the given external conditions 

 linger and become extinct; they are outstripped and overgrown by such as find 

 the environment to their liking. Hence we speak of the struggle for existence. 

 Plants in harmony with their surroundings are the victors, and they establish 

 themselves upon the arena of this encounter. This, briefly, is Darwin's theory of 

 Natural Selection, a theory which marks an advance upon all other theories of the 

 origin of new species. Though many views may be held as to the precise manner 

 of origin and transformation of forms, there can be no diflTerence of opinion as to 

 the significance of the struggle for existence and of the survival in this struggle 

 of tliose forms best fitted by their organization to the circumstances of the environ- 

 ment. 



THE SUBDIVISIONS OF THE VEGETABLE KINGDOM. 



The fact that the savants of ancient times made no attempt to classify plants 

 according to their structural characters is explained by their limited botanical 

 knowledge. Their interest was restricted to such plants as were in use as drugs, 

 poisons, and charms, to vegetables, fruits, and cereals, finally, to such as were 

 of value for decorative purposes and as symbols of religious observances. Nor 

 was the number of these plants considerable. Some five hundred forms were 

 known to Theophrastus (300 B.C.), whilst Pliny (23-79 A.D.) records about twice that 

 number. The characters of these few plants could be retained in the memory 

 for the purposes of comparative investigations, and their recognition depended in 

 large part upon the general impression gained in the ordinary intercourse with 

 nature. Enumerations of plants were based far more on their medicinal or 

 economic uses, on their hurtfulness and beneficence for mankind, than on any 

 structural characters they might possess in common. Even in the herbals of the 

 sixteenth century, containing, as they did, new descriptions and incomparable 

 woodcuts, were the medicinal and economic properties of the various plants still 

 especially emphasized; Botany was still almost exclusively the handmaiden of 

 medicine and agriculture. 



