f 



KEY TO THE GENERA OF TREES IN THE 

 WINTER CONDITION. 



r>aso(l mainly t>n twig and stem characters. The num- 

 ber following the generic name refers to the list number. 



1. I^\)liage leaves persistent and usually e\ergr(.'en. 1. 



1. h'oliage leaves deciduous each year. 11. 



1. h'oliage leaves needle-shaped, subulate, narrowly 

 linear, or scale-like; conifers. •!. 



'1. h'oliage leaves with expanded blades, netted veined. 8. 



■>. With dwarf branches, each bearing "i-o foliage leaves. 



Pinus. (7). 



.■». Without true dwarf branches. 1. 



4. Leaf buds scaly. •'). 



1. Leaf buds not scaly, naked. 7. 



•">. Leaf scar not on a sterigma. i)r()minent. circular: 

 leaves flat. Abies, (o). 



•'•. Leaf scar on a sterigma, the base of the leaf remaining 

 as a scale on the twig. (i. 



<>. Leaves Mat, those on the upper side of the twig much 

 shorter than the lateral ones. Tsuga. (1). 



(!. Leaves more (U- less 4-side(l, si)reading in all direc- 

 tions. Picea. (.■)). 



7. ]^\)liage leaves small, scale-like. a])presse(l, upijosite, 4- 

 ranked, closely covering the twigs which are de- 

 cidedly flattened and fan-like; leaves of two shai)e>. 

 the dorsal and ventral broader and less acute than 

 the lateral ones; scales of the carpellate cone not 

 peltate. Thuja. (8). 



7. Foliage lea\e> small, scale-like, appressed, opposite. 

 4-ranked, usually much elongated, on somewhat 

 flattened branches; scales of the carpellate cone 4-(>, 

 the two upper fertile, not peltate. Libocedrus. ( 1>). 



7. Foliage leaves small, scale-like, appressed. opposite. 

 4-ranked, closely covering the slightly flattened 

 twigs which are not very fan-like; leaves nearly or 

 (|uite similar; scales of the carpellate coue peltate. 



Chamaecyparis. ( l(i). 

 (22 ) 



