My son plotted a graph of average number of seeds in a pod against number of plants per 0.25 square metre. His biology teacher said it should have been joined with a dot to dot (points were close to a horizontal line- which is what I told him to draw). In Chemistry and in teaching other sciences we have always said you don't do dot to dots (except speed-time and distance-time graphs) but either a straight line or smooth curve. What do you say? Is this sort of data an unfortunate exception, that will just confuse the pupils?