== Cannel from Lycopsid spores== 
 I'll add a note that cannel coal comes from Lycopsid (scale tree) spores, accumulating in coal swamp pond bottoms.  Thus cannel coal seams are shallow and often found above other deposits, while the coal itself, being rich in oils, burns long, with a bright yellow flame and little ash. 

 Don't ask me how to cite it, but the source of this information is the National Museum of Natural History, where one reads: 
 "LCYOPSIDS  SCALE TREES.  One of the major plants of the coal swamps, lycopsids sometimes reached heights of 125 feet... Lycopsids are known as scale trees because their bark is marked by scars (where leaves were attached) that reminded coal miners of fish or reptile scales."  And: "SCALE-TREE SPORES.  Scale trees produced spores in such vast quantities that the spores often filled small ponds in the coal swamp.  The remains of these lycopsid spores were transformed into a special type of coal, cannel coal, highly prized for use in fireplaces."  And another sign mentions the high oil content in spore-based cannel coal (don't have quote).  I'm sure there's more complexity to the story that others may want to add, but, however simplified, this is a reliable source!