KEY TO SOME SHRUB WOODS NATIVE TO THE NORTHERN ROCKY MOUNTAINS 



1 Vessels present . . . . 3 



I Vessels not present . . . . . „ „ . . . . . . . . 2 



2 Tracheids with spiral thickenings Taxus brevifolia (p. 8-9) 



2 Tracheids without spiral thickenings Juniperus spp. (p. 8-9) 



3 Rays 3 to many cells in width, often massive, dispersed between uniseriate rays ... 4 



3 Rays 1 or 2 cells in width (rarely 3) 17 



4 Vessels grouped in patterns forming radial or concentric bands or arcs 5 



4 Vessels predominantly solitary or in pairs, except for initial vessels of growing 



season which may be contiguous 8 



5 Vessel bands radial Primus spp. (p. 16-17, 18-19) 



5 Vessel bands concentric or vessels forming arcs 6 



6 Band of cork tissue initiating each growth ring . . Artemisia tridentata (p. 8-9) 



6 Band of cork not present as above . . 7 



7 Vessels in concentric bands, alternating with bands of 



tracheids and fibers ................ Chrysothamnus nauseosus (p. 10) 



7 Vessels in sbight arcs rather than in concentric bands . Chrysothamnus viscidiflorus 



(p. 10-11) 



8 Perforation plates simple „ . . 9 



8 Perforation plates scalariform „ 11 



9 Growth ring distinct; vessels decreasing in size from early to late wood; vessels 



relatively numerous 10 



9 Growth ring indistinct; vessels not changing in size or spacing from early to late 



wood; vessels relatively few and far apart Holodiscus discolor (p. 14-15) 



or Rubus spp." (p. 22-23, 24-25) 



10 Vessels markedly larger in early than in 



late wood Rosa woodsii (p. 20-21) 



10 Vessels not markedly larger in early than 



in late wood Rosa gymnocarpa (p. 20-21) 



II Tracheids and fibers alternating in radial bands . , . Philadelphus lewisii (p. 26-27) 

 11 Tracheids not alternating with fibers as above ..... 12 



12 Vessels forming complete or short concentric bands within growth ring, 



usually 1 vessel in width 13 



12 Vessels not forming such bands, instead being more in diagonal bands 



or diffuse '. . . 14 



13 Bands complete; vessels of successive bands in any 



one growth ring are of similar size Ribes aureum (p. 28-29) 



13 Bands tending to be interrupted not forming complete 

 bands; vessels of successive bands in any one growth 

 not similar in size; the initial vessels usually are 



markedly larger than succeeding ones Ribes cereum (p. 28-29) 



14 Vessels mostly solitary with some small clusters; are randomly dispersed, 



with no clear pattern evident 15 



14 Vessels arranged in diagonal bands or arcs with a few short, tangential bands . . 16 

 15 Growth ring initiated with a band of larger vessels; the 

 vessels become progressively smaller through the 



growing season; vessels relatively few Ribes lacustre (p. 32-33, 34-35) 



15 Growth ring not initiated with a band of larger vessels 

 although the vessels of the last-formed wood are notice- 

 ably smaller than the initial vessels, making the growth 



rings discernible Ribes hudsonianum (p. 30-31) 



4 



