98 ANCIENT PLANTS 



point of connection with the lower types is not seen, but 

 in Poroxylon, which has otherwise a stem anatomy very 

 similar to Cordaites, we find groups of centripetal wood 

 developed inside the protoxylem of primary bundles. 

 For this reason, principally, is Poroxylon of interest at 

 present, as in its stem anatomy it seems to connect the 

 Cordaites type with that of the group below it in general 

 organization. 



GiNKGOALES. — Reference to p. 44 shows that Ginkgo, 

 the Maidenhair tree, belongs to the Ginkgoales, a group 

 taking equal rank with the large and complex series of 

 the Coniferales. The Ginkgoales of the present day, 

 however, have but one living representative. Ginkgo 

 stands alone, the single living species of its genus, repre- 

 senting a family so different from any other living family 

 that it forms a prime group by itself 



Had the tree not been held sacred in China and 

 Japan, it is probable that it would long since have been 

 extinct, for it is now known only in cultivation. It is 

 indeed a relic from the past which has been fortunately 

 preserved alive for .our examination. It belongs ito the 

 fossil world, as a belated November rose belongs to the 

 summer. 



Because of its beauty and interest the plant is now 

 widely distributed under cultivation, and is available for 

 study almost as freely as the other types of living 

 Gymnosperms already mentioned, so that but a short 

 summary of its more important features is needed here. 



Old plants, such as can be seen growing freely in 

 Japan (in Kew Gardens there is also a fine specimen), 

 are very tall handsome woody trees, with noble shafts 

 and many branches. The leaves grow on little side 

 shoots and are the most characteristic external feature of 

 the tree; their living form is illustrated in fig. 66, which 

 shows the typical simple shape as well as the lobed form 

 of the leaf which are to be found, with all intermediate 

 stages, on the same tree. No other plant (save a 



