480 THE UNIVERSE. 



bring on most harassing diseases, tetters, tinese, etc., as the 

 labors of the microscopists of our day have placed beyond a 

 doubt. Similar to these are certain parasitic plants, which 

 are never found except upon certain insects. 



At other times germination takes place under very strange 

 conditions. Vandermonde saw children in whose noses peas 

 had germinated from having been imprudently introduced. 

 Another physician, Brera, mentions having opened the body 

 of a soldier whose stomach was filled with barley which was 

 developing itself there. 



There are two classes of actions to be considered in ger- 

 mination, namely, physiological phenomena, and chemical 

 phenomena. 



Let us first of all examine the former ; we can discuss the 

 others farther on. So soon as ever the seed is confided to 

 the earth it imbibes water and swells. Soon afterwards the 

 integument tears irregularly, and the young plant appears 

 outside. Sometimes, however, this act is effected symmet- 

 rically. The seed presents a kind of lid, or little door, which 

 the young plant opens by pushing it so as to direct itself 

 towards the soil, as we see in the Indian reeds. After that 

 the root sinks downwards and the stem shoots up towards 

 the light. 



This double phenomenon has occupied physiologists a 

 great deal. At first the direction of the roots was attributed 

 to the humidity of the ground, or to its chemical composi- 

 tion. But Duhamel having noticed that young roots did 

 not sink into wet sponges between which seeds had been 

 made to germinate, and Dutrochet having remarked that 

 seeds suspended in boxes filled with earth left them in 



