MR. CHARLES W. J. UNWIN concludes his series of four specialized talks on gardening matters with some advice on the growing of Dahlias. The modern cult of the Dahlia has resulted in developments so surprising that it is hard to recognize in some of the shaggy species that ornament our gardens the trim, formal flower that was their 'ancestor.' In response to a considerable demand, raisers have concentrated on producing types which are free-flowering, which carry their blooms well above the foliage on long, stiff stems, and which have special value as interior decoration.