EXPLANATION OF THE PLATES. 



Plate DLXVII. Pinus contorta. 



1. A branch with staminate flowers, natural size. 



2. Diagram of the involucre of the staminate flower. 



3. A staminate flower, enlarged. 



4. An anther, side view, enlarged. 



5. An anther, front view, enlarged. 



6. A branch with pistillate flowers, natural size. 



7. A pistillate flower, enlarged. 



8. A scale of a pistillate flower, lower side, with its bract, enlarged. 



9. A scale of a pistillate flower, upper side, with its ovules, enlarged. 



10. A fruiting branch, natural size. 



11. A cone-scale, lower side, enlarged. 



12. A seed, enlarged. 



13. Vertical section of a seed, enlarged. 



14. An embryo, enlarged. 



15. A cluster of young leaves, natural size. 



16. Tip of a leaf, enlarged. 



17. Cross section of a leaf, magnified fifteen diameters. 



18. A seedling plant, natural size. 



Plate DLXVIII. Pinus contorta, var. Murrayana. 



1. A branch with staminate flowers, natural size. 



2. Diagram of the involucre of the staminate flower. 



3. A staminate flower, enlarged. 



4. An end of a branch with pistillate flowers, natural size. 



5. A pistillate flower, enlarged. 



6. A scale of a pistillate flower, upper side, with its ovules, enlarged. 



7. A scale of a pistillate flower, lower side, with its bract, enlarged. 



8. A fruiting branch, natural size. 



9. A cone, from a tree of an intermediate form from the Siskiyou 



Mountains, Oregon, natural size. 



10. A cone-scale, upper side, with its seeds, natural size. 



11. A cone-scale, lateral view, natural size. 



12. Seeds, natural size. 



13. Vertical section of a seed, enlarged. 



14. An embryo, enlarged. 



15. Tip of a leaf, enlarged. 



16. Cross section of a leaf, magnified fifteen diameters. 



17. Winter branch-buds, natural size. 



