You should also be aware that a few families until recently 

retained a different ending, but all current books have changed 

these to conform to the rule mentioned

•

The families of exceptions included Gramineae (grass family, 
now Poaceae), Labiatae (mint family, now Lamiaceae), 
Leguminosae (pea family, now Fabaceae), Umbelliferae 
(parsley family, now Apiaceae), Palmae (palm family, now 
Arecaceae), and Compositae (daisy or sunflower family, now 
Asteraceae)

•

You’ll notice that with the name changes, the usual root word 
of the family has also changed. That’s because a current rule 
says that a family name has to be based on a 

type genus

. 

Therefore, 

Poa, Lamium, Faba, Apium, Areca, 

and 

Aster

are all 

genera for the families mentioned above