Today's Word of the Day means...
a type of small leaf found on clubmosses and horsetails, with a single unbranched midrib
A leaf with only one vascular bundle and no complex network of veins. Horsetails and lycophytes (such as club mosses) have microphylls. Microphylls on modern plants are generally small but in extinct phyla the same structures could grow quite large. In contrast to megaphylls, microphylls are thought to have evolved from modifications of a single stem.