THE CULTIVATED POPLARS. 213 



ber but 'is interesting and useful for contrasting with other trees ; 

 leaves very thick, very large and broadly deltoid, much larger 

 and broader than leaves of the cotton wood under like conditions. 



' ' Wobsky Poplar. One of the most distinct of its class ; of 

 rapid growth and open regular habit. As a timber tree it is up- 

 right and valuable, but it seems to be more susceptible to the 

 work of the poplar borer than other kinds and it occasionally 

 loses its foliage in dry places. On account of these weaknesses 

 it will not be largely planted in this section, but occasional trees 

 may often be used to give variety. The leaves are large, ovate 

 heart-shaped, stiff and very flat, of a shiny blue-green color on 

 the upper and a light green on the lower side. Buds large and 

 sticky. The young growth is only slightly angular. 



' ' P. Certinensis \P. laurifolia of botanists] was introduced into 

 this country and disseminated by Arnold Arboretum. It is per- 

 haps the best of the collection for general prairie and ornamental 

 planting in this section ; perfectly hardy even in the severest ex- 

 posures and rarely, if ever, affected with leaf rust which so often 

 checks the growth of the cotton wood. Its timber makes very 

 good siding for buildings and floors, and answers many of the 

 purposes for which pine is generally used. It does not warp or 

 crack like our native cottonwood. It is rather upright in form, 

 with thick leathery leaves and of very rapid growth. It does not 

 grow quite as fast as the native cottonwood nor resist the attacks 

 of the leaf beetle so successfully, but it is a much longer-lived 

 tree and stands close planting very much better. It is grown 

 readily from cuttings, which in our forest plantation made a 

 growth of a trifle aver 12 feet in three years from half-inch cut- 

 tings planted eight inches apart in rows eight feet asunder. 

 The leaves are thick and leathery with a wavy edge. The new 

 wood is strongly angular. [The form of leaf is shown in Figs. 

 7 and 8.] 



"The Populus Petrovski so closely resembles P. Certinensis 

 that I think them one arid the same thing. Professor Budd ob- 

 taided this in Russia and thinks it different from the latter. If 

 this is true it does not show its characteristics until older than 

 any specimen we have. 



