RAY TRACHEID STRUCTURE IN SECOND GROWTH 

 SEQUOIA WASHINGTONIANA 



H. C. Bel YE A 



(with five figures) 



Ray tracheids are essentially a structural element in all woods 

 of the Coniferae, and, as has been pointed out by several writers, 

 the value of their presence or absence in taxonomy is without 

 question. It has also been stated by several writers on this subject 

 that as a wood structure they reach their highest development in 

 their normal occurrence in the Pineae of the Abietineae, particularly 

 in Larix, Picea, Pseudotsuga, and most notably in Pinus, attaining 

 their greatest complication in the dentations and reticulations of 

 the marginal ray tracheary cells of the hard pines. In the other 

 two members of the Pineae, ray tracheids are normally found in 

 Tstiga, but not in Abies. Although DeBary (i) and Penhallow 

 (6) both described them as characteristic of A . halsamea, this con- 

 clusion does not seem to be borne out by the work of Thompson (7) 

 and Miss Holden (4), who both state that ray tracheids are not 

 to be found in this species. Thompson (7), however, reports them 

 as occurring traumatically in A . amabilis and A . concolor. 



In the Taxodineae, while they are entirely absent from Taxo- 

 dium, they are notably present in Sequoia, and have been described 

 by GoTHAN (3) for S. washingtoniana, and for S. sempervirens by 

 Miss Gordon (2) and Jones (5). 



In the Cupressineae they are found in all members of Chamae- 

 cyparis, more or less abundantly in C. nootkatensis, sparsely in 

 C. Lawsoniana, and, according to Thompson (7), only under 

 traumatic stimulus in C. thyoides and C. plumosa. 



In the closely allied genus Cupressus they are much more abun- 

 dant, frequently occurring as an entire ray one to three cells high. 

 In Thuya they are also quite common, and in this genus are invari- 

 ably marginal, with small bordered pits on their tangential walls, 

 and shghtly larger ones on their lateral end walls. In Juniperui 



467] [Botanical Gazette, vol. 68 



