Resinogenous layer

By the aid of the processes described Tunmann claims to have discovered the resinogenous layer in all the plants examined by him. In the course of his investigations he was able to determine various typical forms of the layer. These he divides into three principal types the rod-type (Viola Fraxinus, Alnus), the vacuola-type (Salvia.Hyssopus), and the mesh or grille-type (Rhododendron, Azalea). 

Volatile Oils.— Thesc are volatile odoriferous principles found in various parts of numerous plants which arise either as a direct product of the protoplasm or through a decomposition of a layer of the cell wall which Tschirch designates a resinogenous layer. They are readily distilled from plants, together with watery vapor, are slightly soluble in water, but very soluble in fixed oils, ether, chloroform, glacial acetic acid, naphtha, alcohol, benzin and benzol. They leave a spot on paper which, however, soon disappears. They respond to osmic acid, alkannin, Sudan III, and cyanin stains similar to the fixed oils and fats. 

---