たね

When our oldest was in yochien, a common homework exercise was to come up with a word that starts with a specified kana and then draw a picture of it.

The clever little bugger always tried to pick words whose pictures are easy to draw.  Once, for は, he came up with はり (needle) and just drew a little line.  For た, he chose たね (seed) and drew a little dot.  We made him draw the plant sprouting from it.