12 PlNACEAE 



crescent-shaped leaf-scars with a single bundle-trace, and num- 

 erous round &cars from which foliar shoots have fallen; very 

 small alternate lanceolate entire leaves mostly on deciduous 

 foliar shoots and so simulating pinnately compound leaves; no 

 stipule-scar&; round-ovoid buds with numerous scales; monoe- 

 cious catkin-like or cone-like naked flowers; and rather small 

 globose cones with thick scales each covering 2 winged seeds. 



1. Leaves very short and scale-like, alternately appressed 



on the stem. (Glyptostrobus). T. distichum imbricatum. 

 Leaves lanceolate, chiefly on flattened deciduous sprays. 2. 



2. Trees. 3. 



Dwarf. T. distichum nanum. 



3. Branches spreading. T. distichum. 

 Branches ascending. 4. 



Branches erect. T. distichum fastigiatum. 



4. Foliage green. T. distichum pyramidatum. 

 Foliage yellow. T. distichum aureum. 



THUJA. Arbor Vitae. 



Evergreen shrubs or trees with rather soft brownish duct- 

 less wood without resin-passages ; rather slender twigs; 4- 

 ranked minute scale-like leaves on finally deciduous fan-like 

 foliar-shoots; no stipule-scars; monoecious catkin- or cone-like 

 naked flowers; and small cones with 1 or 2 winged seeds un- 

 der each of the rather thin scales. 



1. Leaves closely appressed. 2. 



Leaves spreading. (Retinospora forms). 13. 



2. Foliar-shoots mostly horizontal. 3. 

 Foliar-shoots vertical. (Biota). 9. 



3. Oblong or conical. 4. 

 Round-topped. 8. 



4. Leaves green. 5. 



Leaves wholly or partly yellow. T. occidentalis lutea. 



Leaves tipped or variegated with white. 7. 



5. Tall. (American arbor vitae). T. occidentalis. 

 Dwarf. 6. 



