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UNIVERSITY OF COLORADO STUDIES 



ia. Bark of trunk^brownish-gray; fertile catkins about 15 mm. (J in.) long. 



Betula fontinalis Sarg. 

 "Canyon Birch" 



ib. Bark of trunk pale gray or light brownish; fertile catkins about 30 mm. (i\ in.) long. 



Betula andrewsii A. Nels. 

 "Andrews' Birch" 



Fig. 7. — Canyon Birch (Betula fontinalis). X£. 



Genus 9. ALNUS, Alder 



This genus is represented by a single species, a tree or shrub growing 

 in clumps along streams. Leaves broadly ovate, doubly toothed. 



Alnus tenuifolia Nutt. 

 "Alder" 



