484 PART III. — THE CLASSIFICATION OF PLANTS. 



(6) Leaves flat ; placental scales longer or shorter than the 



macrosporophylls . Tsuga 



JS. Long and dwarf-shoots. 



1. Placental scales flat ; foliage-leaves borne on both long and 

 dwarf-shoots ; branching of the stem irregular. 



(a) Leaves annually deciduous ; seed ripens in one year . Larix. 



(b) Leaves persistent ; seed ripens in two years . . . Cedrns. 



2. Placental scales thickened externally into an apophysis: 

 foliage-leaves confined to the dwarf-shoots : branches whorled . Pinus. 



1. Abies, the Silver Firs. The foliage-leaves are flat, marked on the under 

 surface with two longitudinal white streaks, and show in section two lateral 

 resin-ducts: the macrosporangiate cone is developed in the axil of a leaf borne 

 on a shoot of the previous year, at some distance from its apex, and when ripe 

 falls to pieces so that the naked axis remains. To this genus belong A. pectinata 

 {A. alba), the Silver Fir, the emarginate leaves of which stand out in a comb-like 

 manner from the branches; A. Nordmanuiaua, from the Caucasus; A. bahamea, 

 which produces Canada-balsam ; A. cephalonica, which grows in Greece, and A. 

 Pinsapo, which grows in Spain, both having pointed leaves which, in the latter 

 species, are borne on all sides of the branches. 



2. Picea, the Spruce Firs. The foliage-leaves are quadrangular, and have 

 two lateral resin-ducts : the macrosporangiate cone is borne terminally on a 

 shoot of the previous year, becomes pendent after fertilisation, thus enabling 

 the seeds to drop out, and then falls off entire. To this genus belong P. excelsa, 

 the Norway Spruce, the leaves of which are compressed laterally ; in some 

 species, however, the leaves are compressed vertically (e.r/. P.omorica, in Servia, 

 and P. ajanends, in Eastern Asia), and are streaked with white on the upper 

 surface. P. alba and 7iigra are the White and Black Spruces of North 

 America. 



3. Tsuga, the Hemlock Firs. The flat foliage-leaves are somewhat chan- 

 nelled above, with a midrib projecting on the under surface. In other respects 

 this genus, more especially the Section Eutsuga, generally resembles Picea. In 

 the Section Eutsuga (e.g. I's. canadensis) the placental scales are much longer 

 than the macrosporophylls ; whereas in the section Pseudotsuga {e.g. Ts. Doug- 

 lasii) the macrosporophylls are as long as, or longer than, the placental scales : 

 in Eutsuga there is a single median resin-duct in the projecting midrib of the 

 leaf. 



4. Larix, the Larches. The deciduous leaves are arranged spirally on long 

 shoots, and also in clusters on dwarf-shoots developed in the axils of the leaves 

 of the long shoots of the previous year : the microsporangiate cones are borne 

 terminally on leafless dwarf-shoots, the macrosporangiate cones terminally on 

 leafy dwarf-shoots. L. europcea is the common Larch, a native of the Alps and 

 Carpathians. The sub-genus Pseudolarix, including the single species Ps. 

 Kaempferi (otherwise Larix Kaempferi), the Golden Larch, differs from the true 

 Larches mainly in that its macrosporangiate cones fall to pieces when ripe : it 

 is a native of China. 



5. Cedrus, the Cedars. This genus differs from Larix in that the leaves, 

 which are arranged in the same way, persist for more than one year, and in 

 that the seed takes two years to ripen. The genus includes three species : 



