The thorny ground. This seed goes further, it takes root. However the good that they gain by the word is overcome by the weeds and thorns of the world. So while above, the stones spoiled the root, now the thorns spoil the fruit. The thorns represent the cares and riches of the world.
Worldly concerns choke the spiritual life right out of the soul.
Worldly cares distract and divert us from our duties and quench affections that are pleasing to God. The good ground. A great encouragement is here for us. It is interesting that some bear more fruit than others. We should aim at the highest mark, seeking to bring forth a hundred-fold.