310 COLLEGE BOTANY 



pels thin and deciduous at maturity. This genus is represented 

 by A. balsamea (balsam or balm-of-gilead fir). 



5. La/rix, leaves flat, usually in fascicles, and deciduous; 

 staminate cones developed from leafless buds ; pistillate cones 

 from leafy buds; cones maturing during first year and pendu- 

 lous, carpels persistent. The genus is represented by L. laricina 

 (American black larch or tamarack). 



6. Taxodium, leaves flat, mostly fascicled and deciduous; 

 staminate and pistillate cones on same branches; mature cones 

 of very thick-angular carpels. This genus is represented by 

 T. distichum (American bald cypress). 



7. Cliamcecyparis, leaves small, scale-like or awl-shaped and 

 closely appressed imbricated ; staminate and pistillate cones on 

 same branches ; mature cones globular, tightly closed but open- 

 ing at maturity. The genus is represented by C. thyoidei 

 (white cedar). 



8. Thuja, leaves awl-shaped or scale-like; blunt, and short, 

 persistent ; staminate and pistillate cones on different branches. 

 This genus is represented by T. occidentalis (arbor vitse or 

 white cedar). 



9. JwniperuSy leaves awl-shaped or scale-like, rigid and 

 persistent; staminate and pistillate cones on small lateral 

 branches; mature cones small, berry-like and covered with a 

 white bloom. This genus includes /. communis (common juni- 

 per), J. sabind, and J. mrginiana (red cedar). 



10. Taxus, leaves flat, rigid and irregularly two-ranked; 

 staminate and pistillate cones axillary ; mature cone berry-like, 

 cup-shaped, globular, pulpy, red and enclosing the nut-like 

 seed. This genus is represented by T. canadensis (American 

 yew or ground hemlock). 



LABORATORY EXERCISES. 



Exercise. Pinus sp. Examine a branch and note the arrangement 

 of the needles. 



Examine a cross-section of a needle. Note its structure and compare 

 with the leaf of a flowering plant. 



