IT.] CONIFERS. 249 



circular disks, which answer to the margins of minute, 

 lenticular, intercellular cavities occurring between the 

 u pits " of adjacent cells. In the Pines and allied species, 

 with spicate flowers, the cotyledons are usually numerous, 

 varying from 3 to 18 ; hence the term polycotyledonous 

 applied to them. 



OBSERVE, also, the different forms and the arrange- 

 ment of the leaves in Coniferas. In Scotch Fir, for ex- 

 ample, there are two forms of leaf, viz., small, brown, 

 scaly leaves on the main branches the internodes of 

 which lengthen out, and in the axil of each of these scaly 

 leaves a single pair of long acicular leaves, sheathed at 

 the base by scale-leaves. The long acicular leaves are 

 borne upon axillary arrested branches. 



In some other species of Pine the arrested branches 

 bear the acicular leaves in fascicles of threes or fives. 

 In Larch (Larix) and Cedar (Cedrus) the acicular leaves 

 are numerous, in dense fascicles. The former species is 

 well adapted to show the true nature of these fascicles of 

 leaves, some of which lengthen out into branches during 

 the summer. Indeed, the fruit-cones occasionally lengthen 

 out in this way into leaf-bearing branches, illustrating, by 

 their serial continuity, the homology subsisting between 

 the bract-scales of the cone and the scale-leaves of the 

 branch. 



The leaves of many species of Pine persist several 

 years : the Larch is deciduous. 



The Pine Family acquires high importance from the 

 number of species which it includes affording valuable 

 timber, and also from the resinous products obtained from 

 several of them. Among those most valued for the sake 

 of their timber are : 



Scotch Fir, affording Yellow Deal the only Pine now 

 native in Britain ; Norway Spruce (Abies excelsa), yielding 

 White Deal, formerly a British tree, as its cones are found 

 in very recent geological formations ; Weymouth Pine 

 (Pimis Strobus), the most valuable timber fir of North 

 America ; Douglas Pine (Abies Douglasii), of which a 

 spar 159 feet in length is erected as a flag-staff in the 

 pleasure grounds at Kew ; Larch, largely used for railway 

 sleepers ; the New Zealand " Cowdi " Pine (Dammara), 

 affording mast spars 200 feet long. The wood of Cypress 



