146 ANATOMY OF THE GYMNOSPERMS 



of development of the resin cells and the resin passages, the rela- 

 tions just explained must be modified with reference to the partic- 

 ular position of Sequoia, and the sequence would then become : 



1. Thujopsis and 5. Libocedrus. 10. Abies. 



Cryptomeria. 6. Taxodium. 11. Pseudotsuga and 



2. Podocarpus. 7- Juniperus. Larix. 



3. Cupressus. 8. Sequoia. 12. Picea. 



4. Thuya. 9. Tsuga. 13. Pinus. 



But it may assist in the general argument to view this ques- 

 tion from another standpoint. Regarding the resin cells and the 

 secretory reservoirs as falling within a definite series, we may 

 apply to the various forms of distribution, and to the various 

 grades of resin reservoirs, arbitrary values of such a nature as 

 to represent our conception of their relative positions in the scale 

 of development as expressed by percentages, thus : 



Resin cells scattering 25.0% 



Resin cells zonate 37-5 



*Resin cells grouped 50.0 



Resin cells on the outer face of the summer wood, as in 



Pseudotsuga and Larix 12.5 



Resin cells on the outer face of the summer wood, as in 



Abies (partial only) 5.0 



Resin cells wholly wanting o.o 



f Resin cysts, as in Tsuga, Abies, and Sequoia 70.0 



Resin passages with constrictions, as in Pseudotsuga, Larix, 



and Picea 80.0 



Resin passages without constrictions and of the highest type 



of organization, as in Pinus 100.0 



We obviously have two subordinate series here, which for 

 convenience may be regarded as conterminous, but which, as 

 already shown, are "faulted" in such a way that the grouped 

 resin cells (*) and the resin cysts (f) jointly represent the point 

 of divergence for two separate courses of development, the 

 latter continuing upward, while the former descend and thereby 

 represent degradation. These features are best exhibited graph- 

 ically, and the accompanying curves clearly show how, on the 

 one hand, resin cysts and resin passages directly result from 



