EXPLANATION OF THE PLATES- 

 Plate SXXIIL Ptelea trifoliata- 



!• A flowering branch, natural size. 



2. Diagram of a fertile flower. 



3. A sterile flower, enlarged. 



4 Vertical section of a sterile flower, enlarged. 



5. Posterior and anterior views of a stamen, enlarged, 



6. A fertile flower, enlarged, 



7. Vertical section of a pistil, enlarged. 



8. Cross section of an ovary, enlarged. 



Plate XXXR^ Ptelea XRiroLiAXA. 



L A fruiting branch, natural size, 



2. Vertical section of a fruit, natural size. 



3. A seed, enlarged. 



4. Vertical section of a seed, enlarged. 



5. An embryo, much enlarged. 



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