ORGANIC STRUCTURE. 



Fig. 35. 



113 



Spiral fibres found in young shoots, petals, and points of some 

 roots. 



These spiral vessels, or rather ligneous fibres 

 spirally disposed, being seen only in young shoots, 

 leaves, petals, &c. which are in the act of elongation, 

 and never after the longitudinal growth is over, may 

 be conceived to act mechanically, as before observed, 

 in the evolution of the shoot ; or, if not, we must ad- 

 mire the natural disposition of a fibre, of perhaps a 

 foot long, so coiled up in a bud before its expansion. 



If we examine a single fibre with a glass we gain 

 no very clear idea of its conformation. However 

 carefully separated from the mass, there remains ad- 

 hering to it a crust of the cellular matter which unites 

 the fibres together, so that its structure is thereby 

 obscured. But it evidently has an identical character, 

 of which its toughness and elasticity are sufficient 

 proofs. Physiologists who have employed micro- 



