70 SIXTEENTH CENTURY. PT. in. 



went on in the old way, collecting and naming plants with- 

 out trying to classify them. Csesalpinus knew about 1500 

 species of plants, 700 of which he had collected himself. 

 He was the first to point out that the use of flowers which 

 have no seed-vessels, but only stamens (or little thread-like 

 stalks, tipped with yellow powder), is to drop the powder or 

 pollen on flowers which have only seed-vessels and no 

 stamens, and by this means to cause the seeds to grow and 

 ripen. Such plants which have the stamens in one flowet 

 and the seed-vessel in another are now called Monoecious, 

 while if the flower containing the stamens grows on a dif- 

 ferent plant from the one containing the seed-vessel, such 

 plants are called Dioecious. 



Chemistry of Paracelsus and Van Helmont, 1520- 

 160O. There is very little worthy of notice in the 

 chemistry of the sixteenth century ; but we must mention 

 in passing two famous men : Paracelsus, who was born in 

 1493 at Einsiedel in Switzerland, and Van Helmont, born 

 at Brussels in 1577. 



Paracelsus was at one time Professor of Physic and Sur- 

 gery at Basle, but he gave up his professorship and travelled 

 about Europe during the greater part of his life. Among 

 other things, he pointed out that air feeds flame, and that, 

 if you put iron into sulphuric acid and water, a peculiar 

 kind of air rises from it. He also succeeded in separating 

 gold out of a mixture of gold and silver by using aquafortis 

 or nitric acid which dissolves the silver and lets the gold fall 

 to the bottom of the vessel. He did not, however, make 

 many discoveries which are valuable now, and he taught a 

 great deal that was absurd and bombastic. 



Van Helmont was also a wandering physician, but as a 

 chemist he was more careful in his experiments than Para- 

 celsus. He seems to have known a great many different 



