50 



IRISH GARDENING. 



POPULUS REGENERATA AT GlASNEVIN. 



(By the courtesy of the Royal Scottish 

 Arbovieiiltural Society). 



is the best known po])]ar. This is not a species 

 or geographical form, but is a pecuHar sport of 

 P. nigra, var. typica, which was unknown until 

 the 18th century. It originated about 1700 as 

 a single tree on the banks of the Po, charac- 

 terised by branches tending to grow vertically 

 upwards, thus forming a narrow crown. It is 

 invariably propagated by cuttings ; and all the 

 Lombardy poplars now spread over the world; 

 are simply slips of the original tree. This 

 happened to be a male tree ; and in eon- 

 sequence, all the trees derived from it bear 

 staminate flowers. The wide-spreading natural 

 form of the typical P. nigra is rarely seen in 

 cultivation in these islands. 



The American species, P. deltoidea, is also 

 extremely rare at the jiresent time in Eiu'ope. 

 In fact, all the black poplars, so commonly seen 

 in cultivation in these countries, and in France 

 and Belgium, which are supposed by many 

 l)otanists to be the American species, are not 

 that species; and are without doubt hybrids 

 between the American and European species. 

 This fact is easily established from their history 

 and a study of their botanical characters. With 

 the introduction, at the end of the 17th cen- 

 tury, of American trees into Europe, hybrids 

 l)etween them and the allied E\u-opean species 

 soon began to appear as natural seedlings in 



nurseries; and in no genus are they so readily 

 l)i()duced as in Populus, where the individuals 

 occur in two sexes. Moreover, hybrid seed- 

 lings are readily noticed, as they are endowed 

 ^\•ith exceptional vigour, and mu'serymen were 

 not slow in propagating these profitable trees. 

 I have else^diere given the history of the dif- 

 ferent hybrid poplars ; and I need here allude 

 only to the best-known and most valuable 

 kinds. The hybrids have leaves intermediate 

 in shape, never shallowly cordate at the base, 

 as in P. deltoidea, and never cuneate, as in 

 P. nigra; the marginal cilia are sparse and 

 irregular; and the basal glands are variable on 

 the leaves of the same branch, absent on one 

 or two; not always present, as in P. deltoidea; 

 nor always absent, as in P. nigra. 

 The principal hybrid poplars are: — 

 1. Populvs scrotina. — A tree with staminate 

 flowers, always known in England as the Black 

 Italian Poplar, a inisnomer, as it originated in 

 France l^efore 1755, and has no connection with 

 Italy. It has non-hairy twigs, and is the latest 

 of all the poplars in unfolding its leaves, which 

 in the young state have a fine bronzy tint. It 

 has ascending branches, and a wide head, and 

 is the commonest poplar in England, where it 





-■..-^■I'lliWihiiliiri Min 



POPCLrS EITGENEI AT KeW. 



(V>y tlio courtesy of the IJoyal Scottish 

 Arl.)oricultural Societv ). 



