RESIN PASSAGES 



141 



Gymnosporangium clavariaeforme, often forms somewhat exten- 

 sive wedge-shaped masses projecting between the rows of tra- 

 cheids (72, 388). A close comparison of such a tissue with that 

 of the resin cysts of Abies shows that the two are essentially 

 the same, and we must therefore conclude that the cell aggre- 

 gates which precede the formation of resin cysts in Sequoia, 

 Abies, etc., are also to be found in Juniperus as a consequence 

 of injury effected by parasitic growths. 



More recently Jeffrey (24) has contributed an important paper 

 on the anatomy of Sequoia, in which he brings out several facts 

 of considerable value. He shows that resin cysts may arise in 

 the roots of Abies balsamea which have been injured, while they 

 may also be produced experimentally by injury, thus confirming 

 the observations of Anderson that they may be traumatic in 

 their origin. The most significant facts, however, relate to the 

 normal occurrence of such cysts in Sequoia. He shows in the 

 first instance that they are absent from the wood of the first 

 year's growth in S. sempervirens, while they are present for the 

 same period of growth in S. gigantea, though absent from the 

 growth of later years. In both species they arise in the earlier 

 spring wood. In the case of S. Penhallowii from the Miocene 

 the same author directs attention (25) to the occurrence of resin 

 passages in both a radial and longitudinal direction, and estab- 

 lishes important relations between them. The somewhat strict 

 localization of the latter and their obvious connection with injury 

 in well-defined instances leads him to the conclusion that they 

 are wholly traumatic. This rule he also applies to all cases of 

 tangentially disposed resin cysts or resin passages such as occur 

 in Sequoia sempervirens, thereby making it include all similar 

 cases in the various species of Abies and Tsuga. 



Some years since, De Bary (13, 490-495) formulated the law 

 that "resin canals occur in the ligneous bundles of the same 

 Abietineas which possess horizontal canals in the medullary 

 rays." This is a law of very great constancy in all those cases 

 in which a canal proper is developed, though it fails in such 

 cases of resin cysts as occur in Abies and Tsuga (59). It also 



