meaning of rhachis
1. The spine.
2. The continued stem or midrib of a pinnately compound leaf, as in a rose leaf or a fern.
3. The principal axis in a raceme, spike, panicle, or corymb.
4. The shaft of a feather. The rhachis of the after-shaft, or plumule, is called the hyporhachis.
5. The central cord in the stem of a crinoid.
6. The median part of the radula of a mollusk.
7. A central cord of the ovary of nematodes.