696 THE AMERICAN NATURALIST. [Vol. XXXVIII. 



Phylogexetic. 



We are now in a position to present an answer to the question, 

 How are the resin passages related to the phylogeny of the 

 Coniferales ? " In order to present an intelligent answer to this 

 question it will be necessary to recall the facts already discussed 

 in connection with the resin cells and bring them into relation 

 with our discussion of the resin passages. 



In the genus Sequoia it has been shown that the general 

 course of development of the resin cells is essentially the same 

 as in Cupressus, etc., while it has also been shown that the 

 genus presents in other respects a somewhat remarkable devia- 

 tion. Of the two existing species, both show the distribution 

 of the resin cells to be of the typically primitive form, i. c., 

 scattering. Nevertheless there are also in Sequoia sanpcrvircns 

 definitely organized resin cysts but without exhibiting the tran- 

 sitional form of a zonate disposition. Among fossil representa- 

 tives Penhallow (41, p. 41) has shown precisely the same fea- 

 ture to be present in 5. langsdorfii. This is the less remark- 

 able, however, because that species is undoubtedly the ancestral 

 form of, and practically identical with, S. scmpervirens. The 

 fact made clear by Jeffrey (24, p. 457), that resin cysts occur m 

 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 presented by Juniperus, since the aggregation of resin cells 

 and the formation of cysts from them has arisen abruptly and 

 without the transitional forms presented by Juniperus and Taxo- 

 dium. 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. In this sense it may be regarded as 

 the terminal member of a developmental series embracing the 

 Taxodiince, Cupressine^e, Taxoide^e as follows : — 



1 . faxus and Torreya. 



2. Thuyopsis. 



3- Cryptomeria. 



4- Podocarpus. 



