130 ANATOMY OF THE GYMNOSPERMS 



certain Coniferas (13, 440), and in order to clearly differentiate 

 them from those which occur in the genus Finns I shall reserve 

 for all such cases the term resin cyst. While such cysts are 

 typically developed in the three genera named, they are also 

 features of Pseudotsuga, Larix, and Picea, --in fact, of all those 

 genera in which the epithelium is composed of thick-walled cells, 

 -but in these latter cases there is the additional feature that 

 such cysts are always accompanied by the occurrence of similar 

 structures in the medullary rays, and therefore they are asso- 

 ciated with fusiform rays. From these facts, then, it is obvious 

 that we have here a group of six genera all characterized by 

 the presence of structurally similar resin reservoirs, but sepa- 

 rable into two groups through the absence, on the one hand, 

 and presence, on the other, of fusiform rays. That such saclike 

 reservoirs represent the primitive form of the resin passage 

 scarcely admits of question when we observe the various transi- 

 tional forms which they present, and the relation which they bear 

 to the resin passages of Pinus, --a view which is strengthened 

 by the observation of De Bary (13, 443) that primitive forms of 

 the secretory reservoir occur in the pith of Gingko in the form 

 of elongated sacs. 



De Bary has shown that (13, 440) the secretory passages 

 traverse the wood longitudinally, at first as prismatic tubes, 

 which usually acquire a round or elliptical transverse section. In 

 its strict sense, this statement is applicable exclusively to the 

 genus Pinus, but inasmuch as there are important structural 

 gradations whereby Pseudotsuga, Larix, and Picea represent an 

 intermediate type, while Pinus represents a completed type, it 

 will be necessary to compare them somewhat in detail. In the 

 genus Pinus, however, the secretory reservoir differs from that 

 of all other genera, in that it consists of a definite and continu- 

 ous canal of indeterminate length, and for the purpose of differ- 

 entiating it from other forms I shall reserve for it the appropriate 

 and long-used term resin passage. 



In Pseudotsuga the resin cysts are always scattering, though 

 they frequently occur in tangentially extended groups of two or 



