Here's why:

* Dicots have two cotyledons (seed leaves) in their seeds, while monocots have only one.

* String beans are part of the legume family, and all legumes are dicots.

* Other characteristics of dicots include:

* Net-like leaf venation (string beans have this)

* Taproot system (string beans have this)

* Flower parts in multiples of four or five (string beans have this)

So, even though string beans are long and slender, they are not related to monocots like grasses.