counting Fatsia

I took these photos because I've always been impressed by the deep chocolate brown that Fatsia leaves go when they eventually wither. 

Fatsia japonica, commonly grown as an evergreen foliage plant in our gardens, is a native of southern Japan and Taiwan. The name Fatsia derives from the Japanese word for "eight" (fatsi, or hachi in modern romanization), and refers to the number of lobes on the leaf. (The Japanese name is yatsude, meaning "eight fingers".)

Which would indeed be a noteworthy thing. Usually leaves have an odd number of lobes, because they have a single terminal lobe produced by the main vein, which is a prolongation of the leaf-stalk. And in fact Fatsia is no exception in this respect. It has a single terminal lobe and a matching number of lobes on each side. So a large leaf would typically have nine lobes, smaller ones typically have seven, or five.

That said, the withered leaf in my photos does indeed have eight lobes, because the lowermost lobe on one of the sides didn't develop; the ninth vein is there, but it formed no lobe. I suppose this is a common occurrence.

It's a rather similar situation to the starry boreal plant Chickweed Wintergreen (Trientalis europaea, aka Lysimachia borealis), whose traditional name is Siebenstern in German and Sjöstjarna in Icelandic; both names mean "Seven-star" and refer to the number of petals. Actually the flowers have a varying number of petals, from 5 to 9. But when it comes to petals, it's seven that stands out as the unusual number.

It's interesting that in both instances ordinary people who were not botanists noticed the unusual number and named the plant from that, ignoring all the counter-examples.

Our ancestors had no scientific understanding of plant life and no systematic or technical vocabulary. They were mostly illiterate, so left few records, had no uniformity of naming from one village to the next, and credited a riot of absurd and inconsistent legends. It's easy to acquire the false impression that they paid plants little attention. Only stray clues, like the number-names Yatsude and Siebenstern, betray the intimacy of their acquaintance with the plant world.