What is the word/the seed in Mark 4?

I'm preaching Mark 4:1-34 this Sunday. It's the parable of the soils, followed by a couple of parables explaining the kingdom of God. The parable of the soils talks a lot about "the word", but it's never explained. This is an attempt to explain what it might mean.

When you look at the many times "the word" (ὸ λογος) is in the New Testament, it's often translated in any way except "the word." It's message, thing, statement - usually something word related - but "the word" is undertranslated. Dr John Davies raised this point in an FBS seminar on Luke's use of λογος, which is really straightforward, but rarely commented on.

So what is "the word" which is sown in Mark 4? It's usually generalised to preaching generally about the kingdom, based on the parables which follow. But I think it's more specific than that.

In preparing for this series, I've enjoyed working through Peter Bolt's NSBT volume, "The Cross from a Distance", which reads the whole of Mark through the lens of atonement. He doesn't really go here (although he does have a footnote referencing N.T. Wright referencing McDonald, 1989), but there are a few things which made me think "the word" here is specifically the message of the cross.

Take for instance the parable of the seed growing quietly (4:26-29). The seed is not just "ripe" (EVV), it is "delivered over" or "betrayed". And it is not just picked, but the sickle is sent in (cf Joel 3:13).
The following parable, of the mustard seed (4:30-32), describes a seed, dead in the ground, which comes to life. This same image is used in 1 Corinthians 15:35-37 to describe the resurrection body.
Bringing it back to the parable of the soils, we can see that the first three soils each point to an element of Jesus' passion.

1. The footpath recalls the path Jesus took, as he was led to his crucifixion, mocked by the crowds (Mk 15:16-22).
2. The rocky soil (πετρώδης) reminds us of Πέτρος - Peter - who thrice withered under the heat of the questioning (Mk 14:66-72).
3. The thorns which choke the word (ἄκανθα) are reminiscent of the thorns which crowned Christ's head (Mk 15:17).

I know these, on their own, are a bit hard to connect, but with the context, and their colocation, I think it's fair to suggest something is being said here.

"The word" then is not a general message, nor is hearing about being generally better listeners. But the message is specifically the atonement and the resurrection, with this being the first of multiple calls to follow the son of man who will suffer, die, and then rise.