Explain the metaphor of seed in chapter 8 of Great Expectations?Charles Dickens's Great Expectations

When Pip goes to stay with Uncle Pumblechook on High
Street in London, he writes,

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...and I wondered when I peeped into one or two
on the lower tiers, and saw the tied-up brown paper packets inside,
whether the flower-seeds and bulbs wanted [needed] of a fine day to break
out of those jails and
bloom

 In an
extension of this metaphor of the seeds being jailed, Pip himself feels sympathy with
them as he is tightly confined in a little bed in the cofining attic with the sloping
roof.  This compartmentalizing of Pip then extends to Uncle Pumblechook and the other
merchants. Albeit a sycophant of the aristocracy, Uncle Pumblechook is yet, like the
others of the middle class, restricted to his own level of
society.

The extended metaphor of the confinement of the
seeds as though they are in jail imitates the societal jail of the merchant class and of
other classes in Charles Dickens's Great
Expectations:  

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I discovered a singular affinity between seeds
and corduroys (that Pumblechook wears)....there was a general air about the corduroy, so
much in the nature of the seeds, and a general air and nature about the seeds, so much
in the nature of the corduroys...that I hardly knew which was
which.

Clearly, then,
Dickens's metaphor of the seeds reminds readers of the motif of society as a prison in
which no one can truly rise above or escape one's class.  Try as he may, Uncle
Pumblechook who aspires to become an aristocrat, can only remain in his "corduroys" with
the seeds that share the "general air."