The Magic of Akutagawa

The story: 魔術 It's become one of my favorite Akutagawa stories, I've now read it numerous times, new discoveries with each rereading. The scene in question involves an act of,what, legerdemain, and Akutagawa's choice of the term 撒き散らす to describe spreading or scattering. Now, 撒き散らす is an unusual choice, in my opinion, as either kanji (撒くor 散らす) by itself would have done. 撒き散らす。So, where's the difference, what's the point?