Image from W.H. Freeman and Sinauer Associates, used by permission.
Dicots have two cotyledons.
Both groups, however, have the same basic architecture of nodes, internodes, etc. Image from W.H. Freeman and Sinauer Associates, used by permission. Note the scattered vascular bundles of the corn stem. Monocot stems have scattered vascular bundles. Dicot stems have their vascular bundles in a ring arrangement.