Watercolor can convey a lot of information with simple means.
Cornelius Varley
This looks like a practice sheet to try different ways of capturing those wind-blown shapes. Each sort of tree has a different silhouette Shape and leafy character.
The studies in this post are by Cornelius Varley (1781–1873), who was a scientific instrument maker by profession. In 1845 he wrote a Treatise on Optical Drawing Instruments.
He painted in watercolor for the pure love of it, creating many of his studies on trips to Wales. This sky study from 1803, making him a very early plein-air practitioner.
