The "bubble tree" paintings are part of a series with many hundreds of circles in them. The circle, orbs or bubbles represent Joy, the circle of life, angelic activity, playfulness , magic and promises to Wendy.
The circle is Aesthetically childlike, almost magnetic like a ball : we are drawn to them. A circle is safe with no sharp edges. Circles are very approachable. Research has shown that curved forms are associated with positivity.