114 THE AMERICAN NATURALIST. [Vor. XXXIX. 
nontoides are contemporaneous with those of the Japanese spe- 
cies. No other evidence has been forthcoming since then, so 
far as I am aware, and the real American parentage of a most 
noteworthy addition to the ornamental trees of this country still 
remains in doubt. Within the last twelve years, opportunities 
have been presented to inquire into the evidence which might 
be secured from an anatomical point of view, and to determine 
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to what extent the external alterations attendant upon hybridi- 
zation correspond with internal structural changes. It was felt 
that the answer to this question might very largely contribute 
to a solution of the difficult problems relating to the origin of 
species by either mutation or hybridization, and admit of a more 
precise limitation of the characters which define a species. The 
