In tension wood of some species a gelatinous layer (G-layer) is formed on the inside of the innermost wall (S1, S2 or S3) \citep{gardiner2014biology}. The G-layer has near vertically oriented microfibrils and very little lignification. It is suspected that the G-layer plays an important role in the generation of reorientation stresses \citep{Pilate_2004}.