Leaf shapes (don't have much to do with families of trees)
After five years of working for a professional society of plant biologists, I am finally educating myself about plants. My mother-in-law gave me The Golden Field Guide to Trees of North America. It is an excellent book, and I've spent many hours staring at the 1950's-era color drawings of trees, leaves, fruits, bark, etc.
I'm struck by the "families" of trees. You may know about the classification systems for living things — the basic level being species, such as the oregon crab apple (Malus fusca) or the Biltmore crab apple (Malus glabrata). The next highest level is genus, such as apple (Malus), ash (Sorbus), and hawthorn (Crataegus) — each having various species within them. Genus and species has always made sense to me.
The next level up (that is, the first of the "higher taxa"), the families, has always been something of a mystery to me — although I've heard of some families and I've even seen them mentioned in articles I've worked on for a living, it hasn't mattered to me what family a living thing belongs to. Now I get it, thanks to a very small amount of study.
When you say a tree belongs to the family Rosaceae, you mean it's part of a sprawling, dizzyingly varied, historically pivotal family of plants that includes more than 3,000 species and dozens of genuses, including the roses we get on Valentines Day, all apples, cherries, plums, pears, almonds, strawberries, blackberries, raspberries, ashes, hawthorns, and more.
When you say a tree belongs to the family Platanaceae, you mean it's a sycamore, also known as a plane tree. The family contains only one genus (Platanus) and about six species.
Now I understand that when one biologist says that such-and-such is in this-or-that family, this may be hugely significant information to an informed listener. This confirms the assertion (of the movie Animal House) that "Knowledge is Good."
