midrib

plural midribs

1. biologyThe strengthened vein down the middle of a flower petal or simple leaf or leaflet.

   The midribs of the immense leaves form one of the most useful articles in these lands, supplying the place of bamboo, to which for many purposes they are superior.

   1869, Alfred Russel Wallace, The Malay Archipelago, volume II, London: Macmillan and Co., page 117

   Synonyms: middle rib, midvein

2. biologyThe continuation of the petiole of a pinnately compound leaf around which the leaflets attach.

   Synonyms: middle rib, rachis

3. biologyThe shaft of a feather.

   1 more example

   They first appear as two ordinary feathers, rather shorter than the rest of the tail; the second stage would no doubt be that shown in a specimen of Paradisea apoda, in which the feathers are moderately lengthened, and with the web narrowed in the middle; the third stage is shown by a specimen which has part of the midrib bare, and terminated by a spatulate web; in another the bare midrib is a little dilated and semi-cylindrical, and the terminal web very small; in a fifth, the perfect black horny riband is formed, but it bears at its extremity a brown spatulate web, while in another a portion of the black riband itself bears, for a portion of its length, a narrow brown web.

   1869, Alfred Russel Wallace, The Malay Archipelago, volume II, London: Macmillan and Co., page 389