Answer: Charcot-Leyden crystals, white blood cells and red blood cells
As Florida Fan mentioned, the C-L crystals are a guise for snow crystals, and the red cells may perhaps represent red delicious apples before man-made ornaments were innovated. I also envision the C-L crystals representing pine needles, perhaps?
I was very pleased to stumble upon this 'tree' when looking for some crystals to photograph. Other than the star, nothing else has been digitally added to this image.
Happy Holidays to all!