

0O 



<^ 0© 0^0 



Fig. 21. Vessel elements in side view and cross section. A, B, Bctitla alba; C, D, 

 Liriodcndron; E, F, Lobelia cardinalis; G, H, Quercus alba; I, J, Pijriis Malus; K, 

 Acer Ncgiindo; L, M, Quercus alba; N, end of vessel element from Lobelia showing 

 perforation indicating derivation of porous vessel from scalariform; O, ends of vessel 

 elements from Lobeliu showing method of union of elements in a series. {From 

 Fames and MacDaniels.) 



44 



