WordNet sense 1 (of a leaf shape; long and narrow):

elongate

WordNet sense 2 ((botany) of leaf shapes; of leaves having no divisions or subdivisions):

simple, unsubdivided

WordNet sense 3 (measured lengthwise):

running

WordNet sense 4 (running or extending in the direction of the length of a thing):

lengthways, lengthwise

WordNet sense 5 (designating or involving an equation whose terms are of the first degree):

additive

WordNet sense 6 (arranged in a line):

lineal

WordNet sense 7 (of or in or along or relating to a line; involving a single dimension):

one-dimensional

WordNet sense 8 (of a circuit or device having an output that is proportional to the input):

analog, analogue