PLANT-LIFEFORMATION. 213 



sent the ascent of the Plant out of the first 

 thallus in which it is not yet differentiated 

 from stem and root. Sometimes it has the 

 motile gift like the sensitive plant, whose 

 caprices have hardly yet been fathomed. The 

 leaf has also its varied inner structure, or cell- 

 ular anatomy; suggestive too is its outer ar- 

 rangement on the stem (phyllotaxy). But 

 any ordering of these details of the leaf we 

 shall have to omit. 



So we conceive the vegetal organism dif- 

 ferentiated into its three chief members- 

 stem, root, foliage which are to be grasped 

 in their order and as a process. In the nor- 

 mal Plant-form this process is going* on all 

 the time. The stem pushes to the earth first, 

 returning to the mother after the first separ- 

 ation of life into the cell or into the thallus. 

 This perpetual movement of the Plant down- 

 ward or perchance backward to its origin is 

 called its geotropism, or the turn to the Earth 

 from which it has to recuperate by incessant 

 draughts of its own elements. But now fol- 

 lows the deeper act. From the sun sprang 

 Mother Earth, who thus on her part has 

 her remoter origin her solar father we may 

 call him, to whom the Plant goes back for 

 radiance which the Earth cannot furnish. 

 This is what has been already alluded to as 

 the Plant's heliotropism. So the stem turns 



