Rules

The board is made of two rows of five holes.

At the beginning, there are in each hole five pieces made of a material called kankar (presumably a mineral used as a construction material, a calcareous laterite with a high lime content).

Each player controls the holes on her side of the board.

At your turn you take all the pieces from any hole on your side of the board and sow them in an anticlockwise sense, one in each hole. After you have sown them, you take the ones in the next hole and keep on sowing with them.

Your turn ends when you put the last piece of a sowing in a hole followed by an empty one.

If the hole following the empty one is not empty, after a player has finished sowing, he captures its contents.

The winner of a game is the one who captures more seeds.

According to the description the game ends when "all the pieces on the board are exhausted"

This is indeed possible, although it is a rather unusual ending. Humphries failed to explain what would happen if a player has no pieces to distribute, while his opponent has still pieces left in his holes.

Similar games (e.g. Bay Khom, Walak-pussa) include the following rule:

The game ends when a player has no legal move and the remaining pieces are captured by his adversary.

The game was played in several rounds, in which holes could be captured, but the exact rules weren't given as "by that time things began to get complicated and I was unable to discover how, if ever, the game ended"."