SECT. IX. CAUSES OF DESCENT. 



fluid in the pendant branches of the Weeping 

 Willow, and other such plants, is enabled to coun- 

 teract the power of gravitation, though not wholly 

 to destroy it ; as its agency is still discernible in 

 the pliancy and feebleness of the pendant shoot, 

 and in the occasional success of inverted cuttings. 



This is certainly as complete a jumble as could 

 well have been made if it had even been attempted 

 on purpose ; and a notable example of the unphi- 

 losophical practice of multiplying causes without 

 necessity. First we are told of the paramount 

 influence of gravitation, and then we are introduced 

 to a cause which is capable of counteracting it, if 

 the branch happens to be pendant. And what is 

 this transcendant cause that overcomes even the 

 agency of gravitation ? It is the supposed existence 

 of valves in the tubes of the bark ; an opinion en- 

 tertained with regard to the sap vessels, at least by 

 some of the earlier phytologists, but long ago ex- 

 ploded, as has been already seen upon the almost 

 uniform evidence of the success of inverted cuttings 

 of the Willow and Poplar. But the same argu- 

 ments are applicable to the tubes of the bark, in 

 which if valves even existed they could seldom be 

 of any use, as the motion of the proper juice is 

 almost always downwards. Would not Mr. Knight 

 have found a cause better calculated to account for 

 the phenomenon of the inverted layer in the force 

 of habit, on which he lays so much stress, in a 

 variety of other cases ? as for example in that of 



