The crop series and like-from-like generation

Meaning

Onion, spelt, barley and oats furnish concrete examples of like arising from like. Rose, nut and lettuce are named as outcomes an onion seed does not yield. The series is not botanical description for its own sake: it supports a broader and false inference about human generation. Far returns at the end of Book 3 in the bread allegedly hostile to honey, linking an ordinary crop to a different explanatory setting.