HEREDITY AND EVOLUTION IN PLANTS 



Fig. 2. — Portion of the rhizome of the common brake {Plcris aquilina) 

 showing a cross-section view at the right. 



Fio. 3. — Cross-section of the rhizome of the bracken fern {Pleris aqui- 

 lina), showing the tissue systems. Greatly magnified. 



