Humulus

1. Main veins of leaf beneath with stiff, spinulose, simple hairs (pustulate-based); petiole about equaling or exceeding the leaf blade; larger blades usually 5–7-lobed; pistillate bracts narrowly acuminate, long-hispid, lacking resinous dots; anthers without resinous dots.

H. japonicus

1. Main veins of leaf beneath glabrous to softly pubescent and/or with a few short stubby 2-hooked hairs; petiole shorter than the leaf blade; larger blades 3-lobed (rarely 5-lobed); pistillate bracts (especially younger ones) broadly acute to obtuse or rounded, glabrous or with tiny hairs, usually with at least a few resinous dots basally; anthers usually with resinous dots.

H. lupulus

All species found in Humulus

Humulus japonicusJAPANESE HOPS 
Humulus lupulusCOMMON HOPS, HOP 

Citation:

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