Nos. 451-452.] ANATOMY OF THE CONIFERALES. 



In radial section the reservoirs are round or oblong cysts of 

 variable size, and they are either contiguous or distant. In the 

 former case they rarely or never become confluent, but they 

 maintain their separate identity as in Sequoia and 1 su.i;a. In 

 the latter case the intervening region is occupied b\ an a,i;>;re- 

 gate of resin cells in all essential respects like those in llie same 

 regions of Sequoia and Tsuga mertcnsiana, or like the a,i;,i;re,-;atcs 

 which are generally characteristic of Tsuga carolifiiaiia. The 

 inner epithelium usually consists of short, cylindrical and stiongly 

 pitted cells which, in the second and third rows, become suc- 

 cessively longer and less strongly pitted, so that those in the 

 outer row may be identical in form and markings with the 

 isolated resin cells. In the two outer rows the ( ells not infre- 

 quently show bordered pits on their radial wallsahus presenting 

 transitional forms which gradually pass over into tracheids, and 

 the one then replaces the other. The parenchyma tracheids, 

 which are always most characteristic of the spring wood, are al- 

 ways distinguished by the presence of large and prominent bor- 

 dered pits, but in addition they are sometimes broad and thin- 

 walled, and lie in radial series. 



From these facts it is clear that the secretory reservoirs of 

 the three genera in question always take the form (jf closed 

 sacs, which DeBary has already pointed out as a feature of cer- 

 tain Coniferae (9, p. 440), and in order to clearly differentiate 

 them from those which occur in the higher Conifera:. I shall 

 reserve for all such cases the term rcsin cyst. That such sac- 

 like reservoirs represent the primitive form of the resin i)assage 

 scarcely admits of question when we observe the various transi- 

 tional forms which they present and the relation they bear to 

 the resin passages of the higher Conifera; — a view which is 

 strengthened by the observation of DeBary (9. p. 443) t^^t 

 primitive forms of the secretory reservoir occur in the pith of 

 Ginkgo in the form of elongated sacs. 



DeBary has shown (9, p. 440) that the secretorv passages 

 traverse the wood longitudinally, at first as prismatic tubes which 

 usually acquire a round or elliptical, transverse section. This 

 statement is applicable to Pseudotsuga, Larix, Picea and Pinus, 

 but inasmuch as there are important differences of detail between 



