Fig. 9.— Structure of a Monocotyledonous Stem, Pondweed {Potamogeton natans) . 

 C. R. Mapp,pJioto-inicro. Seepage 33. 



Fig. 10.— Structure of a Dicotyledonous Stem, Transverse Section of Elm 



C Uhnus catiipestris), 



C. R. Mapp, photo-micro. See page 33. 



