unbranched 
adjective chiefly technical
Not having or divided into branches: a long, unbranched chain of amino-acid residues called a polypeptide...
- The colonies grow as branched or unbranched chains.
- In plants with long unrooted unbranched stems, branching on a phytomer can be induced by the outgrowth of an adventitious root from one of the two root primordia present at its node.
- The vestures in S. japonica vary from small and unbranched to largely branched and widely expanding.