80 Proceedings of the Ohio State Academy of Science 



KEY TO THE GENERA OF TREES IN THE SUMMER 



CONDITION. 



Based mainly on leaf and twiq- characters. The number 

 foUowini;- the g'eneric name refers to the list number. 



1. Foliage leaves with expanded blades, netted- veined. 8. 

 I. Foliag-e leaves needle-shaped, narrowly linear, subulate, 

 or scale-like; conifers. 2. 



1. Foliage leaves fan-shaped with dichotomons venation, a 



number on thick, wart-like, persistent dwarf 1)ranches> 

 Ginkgo. ( I ) . 



2. With typical dwarf branches, persistent for more than 



I year. 3. 

 2. With feather-like dwarf branches, deciduous each year, 

 the linear leaves spreading- into 2 ranks. Taxodium. (7). 



2. Without dwarf branches. 4. 



3. Dwarf [^ranches small, self-pruned, with 2-5 foliage 



leaves. Pinus. (2). 



3. Dwarf branches thick, wart-like, persistent, with nu- 



merous deciduous leaves. Larix. (3). 



4. Leaf buds scaly ; leaves scattered. 5. 



4. Leaf buds not scaly, naked ; leaves opposite or whorled. 7. 



5. Leaf scar on a sterigma, the twigs covered with scales 



representing" the leaf bases. 6. 



5. Leaf scar on the bark ; twigs without scales ; leaves 



flat. Abies. (6). 



6. Leaves flat, those on the upper side of the twig much 



shorter than the lateral ones; trees. Tsuga. (5). 



6. Leaves more or less 4-sided, spreading in all directions. 



Picea. (4). 



7. Foliage leaves small, scale-like, appressed, opposite, 4- 



ranked, closely covering the twigs which are decidedly 

 flattened and fan-like; leaves of two shapes, the dorsal 

 and ventral broader and less acute than the lateral 

 ones ; scales of the carpellate cone not peltate. 



Thuja. (8). 



