PHYSIOLOGY OF TREES. 251 



composed by the action of heat or water. But 

 in no state is it ever found by analysation to con- 

 tain anything like fibrous matter from which 

 organs might be formed; it ever remaining a 

 homogeneous mass, and quite destitute of any 

 special structure to indicate conformation. Chap- 

 tal, indeed, is said to have detected fibrous 

 matter in the sap of some trees; but this solitary 

 instance is not corroborated by any subsequent 

 experimentalist or writer on the subject. 



While occupying its natural station in the 

 plant, we see it at different times more or less 

 fluid. In the spring it becomes exceedingly 

 liquefied, and discharged from wounds as limpid 

 as rock-water; though, if long exposed to the air, 

 it becomes inspissated into gum on stone-fruit 

 trees ; or corrupt like sanies oozing from wounds 

 on the elm. Its motion in the spring and be- 

 ginning of summer is rapid ; but is arrested and 

 congealed by the cold of autumn; and during 

 winter it assumes a clammy consistence, and 

 then only acts like a cement to the fibrous orga- 

 nisation of the new and old wood and bark. 



