664 POPULAR SCIENCE MONTHLY. 



plants before they learn the descriptive terms applied to them. 

 To have a knowledge merely of the names of plants is to possess 

 a series of jug-handles without the jugs or anything in them. 

 The handles belong with the jugs, and jugs should have, at times 

 at least, something in them. Now, the truly scientific man who 

 seems to be devoting his time to acquiring a knowledge of the 

 names of plants, is in reality learning much more about them. 

 He sees that plants of different sorts resemble one another in 

 greater and less degrees. Those which resemble one another, not 

 merely in superficial characters, which may be due merely to like 

 conditions of growth and life, but in the more fundamental and 

 less obvious characters, he assumes are related ; and his studies 

 lead him to formulate a classification which shall indicate in 

 what ways and in what degrees the different plants are related. 

 So we see the first step in the development of botany, the study 

 of plants with a view to arranging them in some classification 

 which shall subserve the convenience of students and at the same 

 time indicate the relationships of plants to one another. But the 

 word relationship implies something more than superficial resem- 

 blance. The resemblance is an index of descent. The older bota- 

 nists Jussieu, Linnseus, and others like them believed that 

 plants are now as they were created created either at the begin- 

 ning of the world or brought into existence later by separate acts 

 of creation. The more critical observations of later years have 

 shown that no two plants are exactly alike, that the offspring 

 are not the duplicates of the parents, that plants are constantly 

 changing as organisms and as generations of organisms. Certain 

 influences cause certain changes ; the different conditions to which 

 plants are exposed in sunny and shaded, in moist and dry, in ex- 

 posed and sheltered positions the climatic, the geological, the 

 geographical conditions all have their effects. And so the study 

 of plants extends from the examination of those just about us to 

 a comparison of these familiar forms with those in other locali- 

 ties. There develops the science of geographical botany, which 

 seeks to penetrate the reasons for the existence of certain plants 

 as characterizing the North American, the central European, the 

 Australian, and other floras. 



In order to solve the problems thus encountered, the botanist 

 must know not merely the present geographical and geological 

 conditions of our globe, or of that part of it which he especially 

 studies, but also what its geological history has been. This throws 

 light upon many questions. For example, the North American 

 flora is much richer than that of Europe. We gain some idea 

 as to the reasons for this when we realize that the last ice period 

 made much of Europe and of North America uninhabitable, as 

 well for plants as for animals. All were compelled to migrate 



