148 ANATOMY OF THE GYMNOSPERMS 



special modification of cell aggregates, while, on the other hand, 

 from the same starting point, there arises a course of degrada- 

 tion which finally results in the complete obliteration of the 

 resin cell as an independent structure. 



The facts thus far set forth have thrown important light upon 

 the general course of development of certain anatomical features, 

 and they also show the general course of development for genera 

 and species with reference to particular structures. They do not, 

 however, convey any information with respect to the origin of 

 the phylum as a whole, or the relations of the particular genera 

 and species from the standpoint of collective data, and such a 

 discussion will be more appropriately reserved for the general 

 summary. There is, however, one feature arising out of recent 

 investigations which calls for consideration at this point, since 

 certain of the conclusions reached are not in harmony with 

 our own, the divergence of opinion indicated being the result 

 of different methods of interpretation. 



Jeffrey states (24, 447, 457) that all such resin cysts as 

 occur in Sequoia sempervirens and Abies are of a traumatic 

 nature, and therefore pathological. To this category he would 

 also doubtless assign the corresponding structures of Tsuga. 

 This opinion appears to be shared by Anderson (1, 2), and it 

 is also apparently supported by Pierce (60). Both Jeffrey and 

 Anderson show that the development of such cysts is sometimes 

 definitely associated with the production of tumors through the 

 operation of parasites, and that they may also be induced by 

 wounds experimentally produced. The facts they cite show con- 

 clusively that resin cysts may and often do arise traumatically, 

 and such is unquestionably true of Sequoia Penhallowii, as shown 

 by Jeffrey (25) within the limits of our present knowledge of 

 that species, but in such cases they lie outside the usual course 

 of development. 



The occurrence of resin passages in the fundamental tissue 

 of the Coniferales is a well-known fact, as pointed out by De Bary 

 (13, 441) many years since, when he summarized the general 

 facts in the statement that " all investigated species of Coniferae, 



