338 



STEM-STRUCTURE 



common ancestral type, is as plainly decipherable as in the 

 Conifers. 



The appearance of the stem in transverse section is very 

 similar to that of a Dicotyledon having secondary growth. The 

 Scotch Fir affords a typical example (Fig. 196, A). Here the 



B. 



FIG. 195. Seedlings of various Conifers. A, Scotch Fir (Pinus sylvestris). 



B, Cypress (Cupressus), showing the two cotyledons and plumule. 



C, Larch (Larix), older seedling which has already produced several 

 dwarf-shoots. Cot., cotyledons ; d.s., dwarf-shoot ; h., hypocotyl. 



irregular outline is due to the adherent bases of the scale-leaves 

 which are occupied by a large-celled tissue (Fig. 196, B), on 

 whose inner side the cork-cambium (Ca.) arises. With the pro- 

 duction of cork, therefore, the epidermis (e.) and the dwarf-shoots 

 become exfoliated, so that the older branches have a relatively 

 smooth surface. The narrow cortex is rather lacunar, and con- 



