250 THE MICROSCOPE. 



subject; and published an excellent paper in the Micro- 

 scopical Society's Transactions) 1840, which contains the 

 results of his observations. 



1 Fig. 156. 



1, Interior cast of the siliceous portion of spiral tubes of the Opuntia. 2, Vertical 

 section of Elm, showing spiral fibre. 



In order to watch the development of the membranous 

 tube of a vessel, no better example can be chosen than the 



; " 







Fig. 157. 



1, A transverse section of Taxus baccata (Yew), showing the woody fibre. 

 2, Vertical section of the Yew, exhibiting pores and spiral fibres. 



