THE SPRUCE FIR 255 



simple primary structure with a small number of 

 strands of wood and bast. This simple primary 

 structure soon becomes completely transformed by 

 the early occurrence of secondary growth on a great 

 scale. The mode of development is like that of a 

 Dicotyledon, and consequently the resulting structure 



pd- 



FIG. 105. Semi-diagrammatic transverse section of a root of 

 Picea excelsa at a later stage, px, pa:,protoxylem groups ; 

 r.c, resin canal; x-, secondary wood ; ph" 2 , phloem ; pc, 

 pericycle ; pd, periderm, formed from outer layer of peri- 

 cycle ; co, remains of cortex. Magnified 22. (R.S.) 



is also similar. We have found many such resem- 

 blances in the vegetative organs, though as we shall 

 see, the two Classes are not at all closely related. 

 The young root is clothed on the exterior by a 

 piliferous layer of thin-walled cells. The root-hairs, 

 however, remain short (Fig. 108, r.h). The Conifers 



