PLANT DEVELOPMENT 



to show for his pains. When the literature 

 and art of Greece and Rome were at their 

 height, something like five hundred species of 

 plants were known and described. When the 

 revival in learning set in, in the Middle Ages, 

 this number had only been doubled ; while in 

 1583, when Shakespeare had nearly reached 

 his majority, only fifteen hundred and twenty 

 plants were known, divided into some fifteen 

 classes. In 1700, under the great impetus of 

 Linnasus, father of modern botany, the num- 

 ber had increased to eight thousand, while 

 today more than two hundred thousand plants 

 are known, named, described and classified. 

 There are fully fifty thousand species of cul- 

 tivated plants alone, embracing thousands of 

 varieties. Even as late as the sixteenth century, 

 most plants were valued chiefly for their 

 known or supposed medicinal qualities. The 

 shape or color of a plant often determined 

 its supposed curative value, as in the case of 

 the hepatica or liverwort, the resemblance 

 to the liver found in its leaves marking it in 

 the mind of the doctors of that day as pecu- 

 liarly helpful for liver complaints. 



Under the light which has developed in the 



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