a tree and drawing instruction online

This is one of the beautiful live oak trees I grew up with, in, under and around. (for scale, it's probably about 35ft tall)
Check out Rebecca Kimmel's paintovers and tutorials. Also check out her Artistic Anatomy and Figurative Art forum at Cgtalk.com

The Structure of Man

Hours of video instruction on drawing the human form from memory. Over 100 short lessons on youtube.