GINKGOALES 



189 



long branch grows rapidly, even half a meter in a year, while a spur 

 2 or 3 centimeters long may be several years old. A spur with its leaf 

 scars and scale leaf scars, and with half a dozen leaves coming out 

 from the top, at nearly the same level, recalls the cycad trunk, with 

 its armor and crown of leaves. 



A spur, even after reaching an age of 5 or 10 years, instead of pro- 

 ducing a crown of leaves, may grow out into a long slender shoot with 

 widely scattered leaves. 



Fig. 201 Fig. 202 



Fig. 201. — Ginkgo biloba: transverse section of long shoot; X8 

 Fig. 202. — Ginkgo biloba: transverse section of spur shoot; X8 



In transverse section, the topography of the long shoot and the 

 spur is very different (figs. 201 and 202). The long shoot has a com- 

 paratively small pith and cortex, its wood is harder, and there are 

 not so many mucilage cavities. Even in old spurs, where the quanti- 

 ty of wood is at its maximum, it is not difficult to cut sections. In 

 both shoots there is an abundant development of secondary cortex. 



Annual rings, while not so prominent as in Pinus and other gym- 

 nosperms of the Chicago region, are well marked. Chicago is near 

 the northern limit for Ginkgo. Seeds planted in the open scarcely 

 ever survive the first winter. The seedlings are kept inside the first 

 winter and then, for several years, are put out earlier and earher in 

 the spring and taken in later and later in the autumn, until they are 

 rugged enough to be set out permanently. Even then the tree is not 

 as hardy as most native trees, for a few weeks of mild weather, too 

 early in the spring, will cause the buds to swell. When cold weather 



