This smallish lycopsid differed from the larger arborescent forms by having a single unbranched stem that grades from vegetative basally to fertile near the apex. 

In this photo you can see the outer portions of both a vegetative and a fertile stem.. 

On the right is a vegetative stem, with large bulbous leaf bases and prominent air channels. 

On the left is the fertile stem.

The string-like structures hanging off of the leaf bases on the left are broken sporangial walls. 

The spores have already dispersed.