CHAPTER II 



GINKGOALES 



THIS group is represented by a single living species, Ginkgo 

 biloba, almost unknown in the wild state, but reported in certain 

 forests of western China. Its extensive cultivation, however, 

 first in China and Japan, and later in all civilized countries, has 

 made it accessible. It was long regarded as an exceptional 

 Conifer of the Taxus group, although its resemblances to Cycads 

 were frequently pointed out. Recent investigation, however, 

 has resulted in regarding this species as the only survivor of an 

 ancient phylum which deserves to be coordinated with Cycads 

 and Conifers. A very full general account of the species has 

 been published recently by A. C. Seward and Miss J. Gowan, 16 

 while two papers by Hirase llf 13 supply the first comparatively 

 full account of the reproductive structures. 



I. THE VEGETATIVE ORGANS 



THE STEM 



The tree has the general habit of a Conifer, with central 

 shaft and widespreading branches (Fig. 27). It is recorded as 

 reaching sometimes a height of more than 30 meters, with a 

 circumference of more than 8 meters. The vascular bundles are 

 collateral, and with a persistent primary cambium as in the Coni- 

 fers, resulting in growth rings of the ordinary type. The sec- 

 ondary wood is composed of tracheids with bordered pits, and a 

 characteristic double leaf trace connects the vascular system 

 of the stem with that of theleaves. Resin ducts are abundant, 

 both in the pith and in the cortex. Two types of branches may 

 be distinguished, the long shoots which are terminal and elon- 

 gate rapidly, and the short shoots which are axillary and slow 

 growing, usually bearing tufts of leaves at the summit, and 

 covered below with old leaf scars. 



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