96 UPTTARD GROWTH OF THE HEAD, AND pt. ir. 



probable that the organisation of the first gemmule of 

 a plant is peculiar ; and I have not a doubt that the 

 first radicle or tap-root of the seedling has a difierent 

 cellular structure from that of the branch or side-roots. 

 If these suppositions are facts, they are very interesting, 

 as showing most clearly and beautifully the hand and 

 design of the Creator. The same physical causes, — 

 that is, moisture and turgescence, drought and exhaus- 

 tion, heat, cold, light, atmospheric aeration, &c., — 

 acting on different cellular organisations, unerringly 

 trace out to each part of the plant the course which it 

 is ordained to pursue. A seed is deeply buried in the 

 autumnal hoard of some animal ; its first gemmule is 

 endowed with an organisation which sends it directly 

 upward. It no sooner reaches the atmosphere than its 

 growth turns wherever it can find hght, which is, in 

 fact, generally wherever it can find room. The seed 

 falls on the surface of the earth, a first root is struck 

 out, whose vertical determination downward nothing 

 can pervert ; though lighter and softer than the earth, 

 it pierces through the earth from above, even without 

 the aid of a foreign fulcrum to press against. When 

 this perpendicular descensus (as the whole root has been, 

 perhaps improperly, called) has, by boring, buried 

 itself, branch-roots strike out, which grow horizontally 

 or vertically upward or downward, or at any inter- 

 mediate angle, according to the level of the ground, 

 at the exact proper distance from the atmosphere 

 which the particular constitution of each plant requires. 



