CHAPTER XXVIII 



SUMMARY OF THE HISTORY AND CHARACTERISTICS OF 

 THE PLANT KINGDOM i 



376. The Plant World Originally Simpler. — Plants as 

 we see them about us to-day are of all degrees of size and 

 complexit)- from bacteria to the highest seed-plants. How- 

 ever, it would be a serious mistake to think of the plant 

 kingdom as always having been as complex as this, or to 

 suppose that the plants which now coexist have always 

 coexisted. Any one looking over the surface exposed in a 

 gravel-pit may perhaps find a stone spear-head made Irun- 

 dreds of years ago (and of a pattern thousands of years old) 

 beside a cartridge shell of last year's model. But unnum- 

 bered generations of men flourished and died between the 

 period of the first spear-head and that of the first metallic 

 cartridge, and both kinds of objects have never been manu- 

 factured in any region at the same time. 



The exact time at which plant life first made its appear- 

 ance on the earth is unknown ; — it must at least have been 

 many millions of years ago.^ The precise kind or kinds 

 of plants which first appeared cannot now be determined. 



1 A large library of books on the topics outlined in this chapter could easily 

 be accumulated. Some important titles may here be referred to by their num- 

 bers as given in the bibliography of Bergen and Davis' Laboratory and Field 

 Manual of Botany, — see numbers 1, 3, 36, 37, 66-70. 



2 In such a brief and elementary presentation of plant evolution as is given 

 in the present chapter conclusions must be stated without much attempt to 

 show the process of reasoning upon which they are based. 



295 



