The Parable of the Good Seed takes up where Jesus' explication to his disciples of the Parable of the Sower leaves off.  Immediately after it come the Parable of the Mustard Seed and the one-line Parable of the Leaven.  Then the author gives the authorized explanation of the Parable of the Good Seed.  

I have put the the verses containing the Parable of the Good Seed in green font, and the verses containing the author's explication of it in brown.  For our purposes, this parable deserves close reading in connection with both the Parable of the Sower and the Parable of the Mustard Seed.  In particular we want to appreciate how it is made clear that the meaning carried by the idea of "seed" in these stories is peculiar to each, and what makes that so.  Also important are the details in verses 34-36 and the last half of verse 43, since these make clear what this particular author's purpose is adopting the parable form.  (I have highlighted these passages in orange.)  You can imagine some quite different purposes a writer might have for taking up this genre.

(Incidentally, you may note that while we are referring to the story here by the name that has become attached to it among English readers of the New Testament, the text itself refers to it only as "The Parable of the Tares."  Our particular text comes from the "King James Version" of the Bible ([1611]).  Readers interested in comparing other versions may consult  The Bible Unbound, a useful site indeed.

24]   Another parable put he forth unto them, saying, The kingdom of heaven is likened unto a man which sowed good seed in his field:

25]   But while men slept, his enemy came and sowed tares among the wheat, and went his way.

26]   But when the blade was sprung up, and brought forth fruit, then appeared the tares also.

27]   So the servants of the householder came and said unto him, Sir, didst not thou sow good seed in thy field? from whence then hath it tares?

28]   He said unto them, An enemy hath done this. The servants said unto him, Wilt thou then that we go and gather them up?

29]   But he said, Nay; lest while ye gather up the tares, ye root up also the wheat with them.

30]   Let both grow together until the harvest: and in the time of harvest I will say to the reapers, Gather ye together first the tares, and bind them in  bundles to burn them: but gather the wheat into my barn.

31]   Another parable put he forth unto them, saying, The kingdom of heaven is like to a grain of mustard seed, which a man took, and sowed in his field:

32]   Which indeed is the least of all seeds: but when it is grown, it is the greatest among herbs, and becometh a tree, so that the birds of the air come and lodge in the branches thereof.

33]   Another parable spake he unto them; The kingdom of heaven is like unto leaven, which a woman took, and hid in three measures of meal, till the whole was leavened.

34]   All these things spake Jesus unto the multitude in parables; and without a parable spake he not unto them:

35]   That it might be fulfilled which was spoken by the prophet, saying, I will open my mouth in parables; I will utter things which have been kept secret from the foundation of the world.

36]   Then Jesus sent the multitude away, and went into the house: and his disciples came unto him, saying, Declare unto us the parable of the tares of the field.

37]   He answered and said unto them, He that soweth the good seed is the Son of man;

38]   The field is the world; the good seed are the children of the kingdom; but the tares are the children of the wicked [one];

39]   The enemy that sowed them is the devil; the harvest is the end of the world; and the reapers are the angels.

40]   As therefore the tares are gathered and burned in the fire; so shall it be in the end of this world.

41]   The Son of man shall send forth his angels, and they shall gather out of his kingdom all things that offend, and them which do iniquity;

42]   And shall cast them into a furnace of fire: there shall be wailing and gnashing of teeth.

43]   Then shall the righteous shine forth as the sun in the kingdom of their Father. Who hath ears to hear, let him hear.