20 TRANSACTIONS OF ROYAL SCOTTISH ARBORICULTURAL SOCIETY. 



5 or 5 inches in width and length ; both surfaces of the leaf 

 and petiole pubescent, some of the pubescence remaining in 

 summer ; basal glands three or four. 



This variety occurs in the south and south-eastern parts of 

 the United States, ascending the Mississippi basin from 

 Louisiana to Missouri ; also in Georgia. 



This large-leaved, more pubescent form is probably the large 

 poplar referred to by Marshall as growing on the banks of 

 great rivers in Carolina and Florida, but I have seen no speci- 

 mens from there. If these turn out to be identical, this form 

 may be considered to be typical Popitlus deltoidea, Marshall. 



I have seen no tree of this variety in Britain ; but it is 

 occasionally cultivated in southern France and in Italy. 



Hybrid Poplars. 



The black poplars which are extensively cultivated for timber 

 in France and Belgium, and also in England, are almost 

 invariably of hybrid origin. This fact is easily established 

 from their history and from a study of their botanical characters. 

 With the introduction at the end of the seventeenth century of 

 American trees into Europe, hybrids between them and the allied 

 European species soon began to appear as natural seedlings 

 in nurseries, and in no genus are they so readily produced 

 as in Fopulus, where the individuals occur in two sexes. 

 Moreover, hybrid seedlings are early noticed as endowed 

 with exceptional vigour, and the propagation of any vigorous 

 seedling poplar by cuttings is so easy that it was often done. 

 I have given elsewhere ^ the history of the different hybrids, 

 and I need only now indicate the characters by which they 

 differ from the parents which are, on the one hand, the glabrous 

 or the pubescent European black poplar, and, on the other, 

 Populus deltoidea. The hybrids have leaves intermediate in 

 shape, never shallowly cordate at the base as in P. deltoidea^ 

 and never cuneate as in P. nigra ; cilia on the margin sparse 

 and irregular ; basal glands variable on the leaves of the 

 same branch, absent or one or two, not invariably -' present as 

 in P. deltoidea, nor always absent as in P. nigra. 



' Trees of Great Britain, vii., 1814 (191 3). 



- In Populus anqulata, the glands are always present, constituting an. 

 exception in this respect to the other hybrids. 



