I had a dream last night about making trees out of parts that snap together. Upon awaking I realized I could print my dream. This had something to do with Tom Love's Visuals but this part is hazy.
I made connectors by displacing and subtracting a conical shape from itself. Two of these are joined by a beam. In my dream these were slanted down. I kept this notion but have not vertically displaced the second connector to simplify printing. enlarge 
My plan was to ring each cone with a bump that would also be subtracted making a positive detent to snap. Friction fit proved adequate for my prototype. enlarge 
2x in linear dimension felt, fit and looked better overall. But 2x is 8x in volume of material and printer time.
module cone(){cylinder(10, 5, 4, true);} module cones(){cone();translate([30,0,0])cone();} module beam(){translate([15,0,0])rotate([0,12,0]) cube([30,2,3],true);} module limb(){cones();beam();} module part(){difference(){limb(); translate([0,0,-5])cones();}}
//scad.fed.wiki/assets/viewstl/viewstl.html?stl=http://scad.fed.wiki/assets/pages/tree-parts/tree-parts.stl HEIGHT 370
See Better Tree Parts where we learn from the dozen parts we've already printed.