GROUP IV. PHANEROGAMIA: GYMNOSPERMJ1. 463 



DIVISION" A. 

 CLASS VIIL GYMNOSPERM^S. 



The plants of this class .are all perennial trees and shrubs, for 

 the most part evergreen : they are classified into the three natural 

 orders, Cycadaceae, Coniferae, and Gnetaceae. 



THE SPOROPHYTE. 



General Morphology of the Vegetative Organs. The body is dis- 

 tinctly differentiated into stem, leaf, and root. 



The Stem grows above ground, usually erect, but climbs in 

 several species of Gnetum : it is woody, and is generally branched 

 monopodially : the symmetry of the main stem is radial, whilst 

 that of the branches is frequently bilateral, either isobilateral (e.g. 

 Thuja, phylloclades of Phyllocladus) or dorsi ventral (e.g. Thujopsis 

 dolabrata, Abies Nordmanniana and concolor, Taxus, Torreya, and 

 many other Coniferae in which the branches are horizontal). The 

 branches in many Coniferae (e.g. Pinus, Sciadopitys, Phyllocladus, 

 Larix, Taxodium, Cedrus, Ginkgo) are dimorphous, being either 

 long shoots or dwarf-shoots (see p. 39) : in Phyllocladus the 

 dwarf-shoots are developed into phylloclades; in the other forms 

 the dwarf-shoots all bear foliage-leaves and fall off, sooner or later, 

 with the leaves which they bear : in Pinus and Sciadopitys the 

 dwarf-shoots alone bear foliage-leaves, whilst in the other genera 

 the long shoots bear foliage-leaves as well. 



The Leaves are either foliage-leaves or scale-leaves. The foliage- 

 leaves are either small and numerous, as in the Coniferae ; or large 

 and few, as in the Cycadacese, and as in Welwitschia where there 

 are only two foliage-leaves : they are branched only in the 

 Cycadaceae: they are sessile in the Coniferas and in Welwitschia: 

 their growth is basal: their form varies considerably, one of the 

 most peculiar forms being that characteristic of certain Coniferae 

 (Abietineae) where the leaf is needle-like (acicular) and either 

 flattened or prismatic and angular. Larix, Ginkgo, Taxodium 

 distichum, and Glyptostrobus, are the only forms in which the 

 leaves fall annually ; in the others the leaves persist for two to 

 ten years, or, as in Welwitschia, throughout the life of the plant. 

 Foliage-leaves are absent in Phyllocladus and generally in Ephedra. 

 A certain amount of heterophylly is observable in some cases : 

 thus the leaves of the shoots bearing flowers sometimes differ from 



v. s. B. H H 



