What is the fine-grained topic of the following text: A story of plants reaching from ancient horsetails (use them for scrubbing pots and suits of armour) through ferns ("Dead bracken, shoved up the chimney and ignited, sets light to the soot and saves bothering with sweeps") and conifers, onto flowering plants and ending among the orchids (some juicy morsels: Military orchids were once known as Soldiers' Cullions - and you will have to go and work out what that means!). Only return the topic.
The historical uses and significance of different plant species.