144 ANATOMY OF THE GYMNOSPERMS 



organized resin cysts, but without exhibiting the transitional 

 form of a zonate disposition. Among fossil representatives Pen- 

 hallow (46, 41) has shown precisely the same feature to be 

 present in S. Langsdorfii. 1 . This is the less remarkable, how- 

 ever, because that species is undoubtedly the ancestral form of, 

 and practically identical with, S. sempervirens. The fact made 

 clear by Jeffrey (24, 457) that resin cysts occur in the first 

 annual ring of vigorous branches of adult trees, as well as in 

 the roots of S. gigantea, also tends to make it apparent that the 

 genus presents a very striking advance upon even the type 

 exhibited by Juniperus, since the aggregation of resin cells and 

 the formation of cysts from them has arisen abruptly, and with- 

 out the transitional forms presented by Juniperus and Taxodium. 

 While, therefore, Sequoia is obviously related to Thuya and 

 Cupressus, on the one hand, it is, on the other hand, related to 

 such types as Abies. 2 In this sense it may be regarded as the 

 terminal member of a developmental series embracing the Taxo- 

 diinae, Cupressineae, Taxoideae, as follows : 



1 . Taxus and Torreya. 6. Thuya. 



2. Thujopsis. 7. Libocedrus. 



3. Cryptomeria. 8. Taxodium. 



4. Podocarpus. 9. Juniperus. 



5. Cupressus. 10. Sequoia. 



In the Abietineae a new series is presented. This is not in 

 any sense strictly conterminous with the first, but the two appear 

 to make a fault, as it were, whereby there is a lateral displace- 

 ment, but of such a nature that Sequoia still serves as the con- 

 necting link. Within the eleven species of Abies investigated 

 three important phases are presented, - - (i) resin cells scattering 

 on the outer face of the summer wood, (2) resin cells grouped 

 and forming cysts, and (3) resin cells entirely wanting. Viewing 

 these phases in the order given, it is to be observed that in those 



1 While Jeffrey has shown (25) that in S. Penhallowii the resin cells are nor- 

 mally confined to the outer face of the summer wood. 



2 This latter relation has been recently emphasized by Jeffrey (25) through 

 studies relating to S. Penhallowii, and it is in direct confirmation of conclusions 

 already reached by Penhallow (44) on the basis of other data. 



