HYBRID TREES 
Many Natural Hybrids, as Well as Sports, to Be Found—Artificial Hybridization 
Leads to Production of Trees Valuable for Their Great Vigor— 
What Has Been Done and What May Be Done 
A Review By W. H. Lams 
United States Forest Service, Washington, D. C. 
orchard trees is now a _ well- 
established art, but breeding 
timber trees has hardly been 
undertaken. The importance of such 
work is being recognized, however, and 
Prof. Augustine Henry has made a 
notable contribution in his study of 
natural and artificial hybrids.' His 
recent paper on the black poplars? offers 
some excellent examples of the occur- 
rence of natural hybrids and the value 
of artificial ones. 
The cultivated species of Populus 
which have been found desirable for 
commercial plantings, he points out, are 
without exception of “unnatural” origin, 
in that they are either sports or hybrids, 
and not ordinary species. 
“A sport is usually a solitary phenom- 
enon, arising either as a sporadic peculiar 
seedling from a seed, or developing out 
of a bud ona tree as a single branch with 
some peculiarity of twig or leaf. A 
sport may be looked upon as a freak, 
not forming the starting-point of a new 
species, but speedily becoming extinct if 
left to nature. Sports, when of interest 
on account of the curiosity or the 
beauty of their appearance, are propa- 
gated usually by grafts, 
layers; being only in rare cases per- 
petuated by seed. Some sports are 
due to arrested development. The tree, 
in the course of its life, often passes 
through stages, like those of an insect. 
The seedling of many species differs 
from the adult tree as a larva from a 
butterfly. The infant ash has simple 
BR eeiert short-lived plants and 
cuttings, or 
leaves. The sport known as the simple- 
leaf ash is simply a seedling ash, which 
has never progressed to maturity and 
may be called a persistent larval form. 
The Irish yew was found in 1767 as a 
seedling on the mountain behind 
Florence Court in Fermanagh, and is 
characterised by all the branches being 
directed vertically upwards and all the 
leaves spreading radially around the 
twig. This is apparently also the 
seedling stage preserved. All the 
myriads of Irish ‘yews, now scattered 
throughout the world, are cuttings either 
from the original tree at Florence Court 
or from trees that were derived from 
those cuttings. 
THE LOMBARDY POPLAR 
“This upright, so-called fastigiate 
form may occur as a sport in any 
species, the best known being the 
Lombardy poplar, which originated on 
the banks of the Po about 1700 and 
subsequently spread over the world. 
The Lombardy poplar and Irish yew 
are striking examples of the immense 
number of individual trees of a sport 
that may exist, this abundance being 
entirely due to human agency. Left 
to nature, these two remarkable forms 
would never have multiplied, and would 
have ceased to exist, once the original 
trees had succumbed to old age or 
injury. The fastigiate sport is of rare 
occurrence in most genera, usually only 
a single original tree being recorded. 
Amongst, however, the cypress and 
juniper families, fastigiate seedlings are 
1 Henry, Augustine, ‘The Artificial Production of Vigorous Trees, ’’ Jour. of Dept. of Agric. and 
Tech. Instr. for Ireland, XV, 1, 1915. 
Xe 2 AprlsdO0s. 
2 Henrv, Augustine, 
“The Black Poplars.’ 
Reviewed by W. H. Lamb in Proc. Soc. Am. Foresters, 
Trans. Royal Scot. Arboricult. Soc., pp. 14-27, 
January, 1916; also in Gard. Chron. (London), LVI, pp. 1, 46, 66, July, 1914. 
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