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The Ohio Journal of Science [Vol. XVIII, No. 4, 



under ideal conditions only the one set of spores and organs to 

 be expressed, although the hereditary abilities for the other set 

 are all present. The morphological expression is brought about 

 in the same way as such a differential development takes place 

 in the tissues of bisporangiate sporophytes, either with 

 monecious or bisporangiate flowers. 



Explanation of Figures 20-26. 



Fig. 20. A staminate flower, with oerianth removed, from a carpellate tree of 



Acer platanoides L. 

 Fig. 21. Part of the same flower, showing the vestigial gynecium. 

 Fig. 22. Staminate flower, wiili perianth removed, from a staminate tree of 



Acer platanoides L. 

 Fig. 2-3. Part of the same flower, showing the vestigial gynecium. 

 Fig. 24. Fruiting carpellate flower, with perianth removed, from the same tree 



as Fig. 22, showing normal young samara and vestigial stamens. 

 Fig. 25. Tip of a staminate flower of Rumex acetosella L., showing one of the six 



stamen filaments and the small vestigial gynecium with three minute 



vestigial stigmas. 

 Fig. 26. Gynecium from a carpellate flower of Rumex acetosella L., showing one 



of the three, large, branched stigmas, the other two being removed. 



I 



