228 ANATOMY OF THE GYMNOSPERMS 



6. * * S. Penhallowii, Jeffrey 



" Transverse. Rings of growth rather narrow, with sharply marked but thin 

 summer wood. Rings regular, or if varying in thickness, varying uni- 

 formly and without violent transitions except as the result of injury. 

 Resin canals present in both the vertical and horizontal planes appar- 

 ently only as the result of injury. The resin canals when present 

 surrounded by resin cells, containing dark brown resin. Resin cells 

 inconspicuous and confined to the face of the summer wood, except 

 in the case of injury, where they may be present throughout the zone 

 of annual growth. Tracheids of the spring wood very large and with 

 pits on the radial walls only. Tracheids of the summer wood with 

 tangential pits." 



"Radial. Rays without tracheidal cells, but with distinctly differentiated 

 marginal cells. Lateral pits of the ray cells elliptical, bordered, larger 

 in the marginal cells. Rows of pits single in the central cells of the 

 ray and 2-3 seriate in the marginal cells. Medullary ray cells covering 

 1-4 tracheids, the central ones resiniferous, the marginal generally 

 empty, sometimes containing large clinorhombic crystals inclosed in 

 cysts derived from the cell walls. Marginal cells with undulating free 

 border, deeper than central cells. End walls of the cells of the medul- 

 lary rays very strongly pitted. Longitudinal walls of ray cells also 

 pitted and rather thick. Rays contain resin canals in the case of 

 injury, which take their origin from similar vertical canals running in 

 the wood. Resin canals of the rays sometimes ending blindly and 

 sometimes in a more external series of vertical canals, often extending 

 through many annual rings, varying greatly in size and frequently 

 occluded by thyloses. Spring tracheids generally with 2 rows of oppo- 

 site pits, which often alternate in the ends." 



" Tangential. Rays of one kind only in uninjured parts of the wood. Fusi- 

 form rays present with linear rays in the case of injury and varying 

 greatly in size. Fusiform rays, when present, generally with central 

 resin canal, which is often occluded by thyloses. Linear rays varying 

 greatly in depth. No pits on the tangential walls of the spring tra- 

 cheids. Pits on the tangential walls of the summer tracheids numer- 

 ous, generally not in rows " (Jeffrey). 



Material but slightly silicified and showing little alteration through decay. 



From a waterworn fragment of a trunk originally 6 feet or more in 



diameter. 

 Miocene(P), from Tunnel No. i, Central Pacific Railway, at Blue Gap, 



Sierra Nevada Mountains (Jeffrey). 



10. * CUPRESSUS, TOURN. PLATES 38 AND 39 



Transverse. Summer wood usually very thin, often barely distinguishable, 

 the structure of the growth ring open throughout. Resin passages 

 wholly wanting. Resin cells prominent, rather numerous in bands, 

 scattering or even apparently wanting. 



