Isotrema

1. Petioles and peduncles glabrous; leaves essentially glabrous beneath.

I. macrophyllum

1. Petioles and peduncles densely hairy; leaves densely hairy beneath.

I. tomentosum

All species found in Isotrema

Isotrema macrophyllumDUTCHMAN'S PIPE, PIPE VINE 
Isotrema tomentosumWOOLLY DUTCHMAN'S PIPE, PIPE VINE 

Citation:

MICHIGAN FLORA ONLINE. A. A. Reznicek, E. G. Voss, & B. S. Walters. February 2011. University of Michigan. Web. March 29, 2017. http://michiganflora.net/genus.aspx?id=Isotrema.