Teratological fruits of Ptelea 
J. ARTHUR HarrRIs 
(WITH PLATE 17) 
For the most part the literature of plant teratology is composed 
of purely casual observations, chiefly records of bizarre structures 
which have caught the attention of the observer who contented 
himself with describing and theorizing. But the work of Magnus, 
Masters, Penzig, de Vries, Véchting, and some others has shown 
that teratology can be taken up as a problem for serious and 
continued work, and with profitable results. 
Some years ago I became much interested in certain problems 
involving the frequency and degree of development of plant 
anomalies commonly classed as teratological. Among the things 
it is desirable to determine concerning teratological structures 
through the examination of large series of material are: 
Frequency of occurrence. 
Range of variability in development. 
Continuity or discontinuity in development. 
One of the series of material upon which observations were 
begun in the winter of 1907 I have not found time nor opportunity 
to continue and the data are put on record here for the benefit 
of anyone occupied with problems of this kind. 
Several observers have described trimerous fruits in Ptelea 
trifoliata, as Roeper,* Schimper,} and Masters.t As material for 
further work I used the numerous fruits of eleven shrubs growing 
in the North American Tract of the Missouri Botanical Garden. 
Two objects were in view. First, to gain some rough approxima- 
tion to the frequency with which anomalous fruits occur. Second, 
to ascertain whether the limit of variability of the fruit is reached 
with the typical two-winged and three-winged forms, and especially 
to find by extensive series of countings whether there is perfect 
* Roeper, J. Linnaea 2: 85. - 1824. ae 
Schimper, C. Flora 12: 433. 1820. 
t Masters, M. T. Vegetable Teratology 364. 1869. 
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