140 



ANATOMY OF THE GYMNOSPERMS 



spring wood of successive growth rings. In the development 

 of such secondary features the cysts manifestly exhibit a dis- 

 tinct approach to that higher type of structure and distribution 

 which is exhibited in Picea. In the following year Anderson 

 (2, 336) further showed that, while resin cysts are absent from 

 the normal wood of A. balsamea, they do arise under the influ- 

 ence of the special stimulus connected with the formation of 

 tumors produced by the action of yEcidium elatinum. He fur- 

 thermore points out that such cysts attain their greatest devel- 

 opment and largest number in the region of greatest stimulation, 

 i.e. in the middle of the tumor, 1 decreasing above and below 

 until they eventually become pointed and finally disappear be- 

 tween four tracheids "which, in their meristematic condition, prob- 

 ably function as epithelial cells." It is unfortunate that the 

 histological details of these cysts and their endings are not given, 

 since such facts would serve to throw much light upon the rela- 

 tion of the cysts to similar structures in normal tissues, but 

 there is no reason to suppose that they differ in their essential 

 structure from those which occur in the normal tissues of the 

 same or other species. The tracheids above referred to are un- 

 doubtedly parenchyma tracheids, and it is probable that further 

 examination would show that they ultimately replace the resin 

 cells remaining over after the disappearance of the cyst proper. 



Tubeuf has also shown (72, 44) that resin canals are irregu- 

 larly formed and greatly multiplied through the action of para- 

 sites, quoting the case cited by Hartig in which the resin canals 

 of the* spruce were found to be so numerous in trees attacked 

 by Agaricus melleus as to give rise to an abnormal production 

 of resin, which flows from the roots and characterizes the disease 

 called resin gland or resin flux. He also points out that a 

 similar flux occurs in the bark of the pine, due to the action of 

 Peridermium pini. The action is therefore developed in such 

 a way as to induce a greater activity in the formation of wood 

 parenchyma, which, in Juniperus communis, when attacked by 



1 A precisely similar relation in development has been noted by Jeffrey (25) 

 in the case of Sequoia Penhallowii. 



