{To face p. 08. 



Fig. 51.— A PiioTOMiCKOfiKAPH iiF Portion of .\ TitAN.svER.sE ,Sk(Tiun 

 ACROhS A Root of Pinux to show the tracheides of the xylem in 

 section. — In the centre is seen tlie tri-radiate protoxyleni, and enclosed 

 between the Y-shaped arms of this three large resin-oanals. 



