Wondering about mimosa and bucks.

Last evening as the sun was setting, I took two pictures of a couple different mimosa shrubs that grow around my place.  The light wasn't very good but I still think they are a bright and joyful view to look upon.  This first one was just behind the dog's back yard:

This one was in the shade behind where the motor-home is parked:

 Sorry about the lighting.

I got wondering how the dollar bill became known as a buck.  Anyone care to guess?  This is what my book, IMPONDERABLES, has to say about it and it also explains the expression, "pas the buck".

"Buck has meant "male deeer" since the year 1000 in England and has meant "a dollar" in Ameria since 1856.  Despite the time gap, the two meanings are closely linked.  In the early eighteenth century, traders and hunters used buckskin as a basic unit of trade.  Any frontiersman who possessed many buckskins was considered a wealthy man.
 
   How did buck come to mean specifically one dollar?  In the early West, poker was the diversion of choice.  A marker or counter was placed to the left of the dealer to indicate who was the next to deal.  This marker was traditionally called the buck, because the first markers were buckhorn knives.  But in the Old West, silver dollars (i.e., one dollar) instead of knives were used as bucks.
 
   The buck as poker counter yeilds the expression pass the buck, a favorite of politicians and bureaucrats everywhere, who usually are more than happy to evade responsibility for governing, dealing poker, or just about anything else, which was why it was surprising to hear Harry Truman, an admitted poker player, announce, "The buck stops here.""

 The above came from my book, but I watched a show on the History channel that had a segment on this subject and said just about the same thing.  When the buck or buck-knive stopped at you, you had the responsibility for the deal.  So, now you know what happens when the buck stops at you and what you are suppose to do. . . No, heck, don't take responsibility, pass the buck (grin).  Now have a great day, you hear?