PHYTOGENY. 219 



1100. The perpendicular direction of the stalk is, 

 however, as mechanically determined by gravity as the 

 root. Paradoxical as this assertion may appear, it is 

 still correct ; for if we think of a moist globe, which is 

 superiorly affected by air, light and heat, the upper 

 aqueous or mucous parts are thus lighter, and necessarily 

 ascend upwards through the pressure of the heavy or 

 unheated parts, just as the air-bubbles in beer ascend to 

 the surface. The light it is true can draw them some- 

 what sideways, chiefly because this side is more heated, 

 more decomposed, and also undergoes a greater amount 

 of evaporation ; but the proper cause invariably resides 

 in the ascent of the light parts between the heavy or 

 immoveable. The stalk therefore grows upwards also 

 in the darkness, and then indeed quite perpendicularly, 

 because it has not been diverted by light. Were the 

 light merely the Dirigent, it could not be comprehended, 

 why towards the poles trees still stand tolerably perpen- 

 dicular, and do not lie completely upon the earth. Were, 

 however, the air that which determines the direction, 

 plants could not thus have been inclined towards the 

 sun, nor could we comprehend why the flowers and also 

 the leaves obey the sun's course. Finally, were neither 

 air nor light the imparters of direction, then the plant 

 could shoot in no other direction than quite perpen- 

 dicularly upwards, as is done too for the most part by the 

 fungi. 



1101. The icinding of the stalk appears to originate 

 from the rotation of the sun. The next cause is 

 probably the greater heating and decomposition that 

 occurs upon one side. In accordance with this assump- 

 tion the plants upon the northern hemisphere of the earth 

 must wind spirally upwards from left to right, or from 

 morning towards evening, if our gaze be directed towards 

 the meridian, but inversely upon the southern hemi- 

 sphere. But this is not the case. May we therefore 

 conjecture that plants, twisted contrary to rule, have 

 been transported from their native soil ? 



1102. The kinds of stalk follow also, without doubt, 



