Tom Chudleigh designed and built the free spirt spheres. They are hand made wooden structures which are held up by a web like attachment to whatever structure is close and strong enough to hold it up. The spheres are made of cedar strips like a sailboat. The idea being that the sail boat is both sturdy and light in weight.

This is potentially important to our project as we are designing an outer shell which will need to be lightweight and also protecting from the outside elements. A window would be incorporated to ensure that there is enough natural light allowed in to the sphere and using inspiration from the design of a sail boat will make it robust and also lightweight.

We would avoid proven mistakes in this kind of project which include making it too rigid. Tree houses need to have some flexibility as they will be hit by wind and rain, they need flexibility provided by the web like attachments mentioned earlier. 

http://www.cuded.com/2012/10/tree-houses-by-pete-nelson/

https://weburbanist.com/2014/02/17/modern-tree-houses-14-awesome-arboreal-dwellings/2/