I56 THE AMERICAN MIDLAND NATURALIST 



TERATOLOGICAL NOTES. 



BY J. A. NTEUWLAND. 



TOXICODENDRON 



The leaves of Toxicodendron vulgare Miller, also Toxicodendron 

 radicans (Linn) Kuntze are ordinarily pinnately trifoliate. Leaves 

 with five leaflets are, however, not uncommon. These are of two 

 rather distinct types, and intermediate forms between terriate and 

 quinate in all stages from the simple leaflets to deeply lobed cleft 

 and divided are even more common. 



The first kind of quinate leaf is that in which the two basal 

 leaflets of the ternate have each apparently given rise by cleavage 

 to another smaller one. The whole has in this case a more decidedly 

 palmate appearance as the petiolules of the outer smaller leaflets 

 come from the same point on the rachis as the larger ones from which 

 they are supposed to have arisen by division. The other example 

 shows two leaflets apparently cut off from the lateral basal lobes 

 of the terminal leaflet. In this way a rather pinnate aspect results, 

 as the two original basal leaflets are inserted at some distance below 

 that of the other three. 



On the supposition, if it can be maintained, that teratological 

 forms may illustrate a reversion of form to an original ancestral 

 common to several present-day types, it may be inferred that the 

 real poison ivy plants show a close relationship to the typically 

 pinnate leaved Toxicodendron Vernix (Linn) Kuntze or Poison 

 Sumac, by postulating a common ancestor for both. The abnormal 

 leaves of the poison ivies referred to above resemble somewhat the 

 more simple ones of 7. Vernix in appearance. Quinate leaves of 

 7 . Vulgare and T. radicans are quite common at Notre Dame. A 

 considerable number of specimens with intermediate forms was 

 collected at Grand Beach, Mich., in the Dune region of Northern 

 Indiana and Southwestern Michigan during the season of 191 7. 



DATES OF PUBLICATION 



No. 3, Vol. V., pp. 55-02-a, 1>., May i,s, 1917. 

 No. 4, Vol. V., pp. 93—112, July 11. 1917. 

 No 5 Vol. V , pp. 1 13 140, I <-'"i ei 5, 1917 



