Lamb: Hybrid Trees 
common; and the upright habit appears 
to come true from seed. The Mediter- 
ranean cypress has been known in this 
peculiar narrow form for centuries, but 
always cultivated. In the wild state, 
as in the mountains of Cyprus, the tree 
is widespreading in habit. The common 
juniper, however, is often fastigiate in 
the wild forests of Scandinavia. This 
exemplifies the difficulty of strict defini- 
tion in nature, as the fastigiate habit, 
which is a rare sport in most trees, 
becomes in the junipers and cypresses 
almost a normal form, capable of being 
perpetuated by seed.” 
If sports among forest trees are more 
common than has been generally sup- 
posed, the same is true of hybrids. 
Prof. Henry mentions the hollies of 
Great Britain, which include numerous 
hybrids and sports, as well as good 
species. American naturalists are famil- 
iar with the hawthorns, whose hybridity 
has lately been demonstrated by Prof. 
E. C. Jeffrey of Harvard and his pupils.® 
The extraordinary state of affairs in 
the hawthorn genus (Crataegus) may 
best be realized if we recall that more 
than 700 alleged species of Crataegus 
have been described, whereas, of all 
other trees in the United States put 
together, there are only some 600 species. 
HYBRID OAKS 
The willows are known to hybridize 
widely, and the various species of oaks 
readily cross with any of their near 
relatives that happen to be growing 
near. Prof. Henry cites an interesting 
oak hybrid in England: 
“The results of the experimental 
sowings of the seeds of numerous elms 
which I made in 1909, together with an 
investigation into the history of the 
Lucombe oak, given in a paper read by 
me at the Linnean Society on the 
seventh of April, 1910, threw new light 
on many hybrid trees in cultivation, 
which had not previously been recog- 
nized as such, in spite of the fact that 
no one could find these trees anywhere 
in the wild state. The statement often 
made that a particular tree was a 
‘variety of garden origin’ was no 
3Standish, L.M. What is Happening to the Hawthorns? 
6, pp. 266-279, June, 1916. 
Sih 
explanation. The Lucombe oak was 
observed in the Exeter Nursery in 1765 
as a seedling, which differed from its 
parent, a Turkey oak (Quercus cerris), 
in being much more fast in growth and 
in retaining its leaves during winter till 
March. Lucombe propagated this seed- 
ling by grafting, and believed it to be 
simply a sport of the Turkey oak. 
In 1792 it bore acorns from which 
numerous seedlings were raised, no two 
of which were alike, while some strongly 
resembled in bark and leaves the Cork 
oak (Q. suber). Lucombe’s son then 
correctly surmised that it was a hybrid— 
the flower on the Turkey oak, from 
which the acorn producing it was 
formed, having been fertilized by the 
pollen of an adjoining large Cork oak. 
“This case illustrates several well- 
known laws in regard to hybrids: 
“1. The first cross is usually of excep- 
tional vigor, more vigorous than either 
parent. 
“2. When the first-cross reproduces 
itself by seed, the second generation 
consists of classes of individuals, which 
differ from one another and from their 
parent. The first-cross never comes 
true from seed, but produces a mixed 
and varied offspring. 
“3. None of the individuals of the 
second generation equal in vigor the 
first-cross. This was also clearly estab- 
lished in the case of the Lucombe oak. 
“Other common trees, of which no 
history is recorded, doubtless originated 
in the same way as the Lucombe oak, 
namely, as chance seedlings (the result 
of accidental crossing by wind or an 
insect), which observant nurserymen or 
-gardeners found desirable to propagate 
on account of their vigor. The intro- 
duction in quantity into Europe during 
the seventeenth century of North Amer- 
ican trees, which grew alongside similar 
but distinct European species in parks 
and gardens, was the occasion of con- 
siderable hybridization. Trees like the 
black Italian poplar and the London 
plane, which have nowhere been seen 
wild, are intermediate in botanical 
characters between an American and a 
JOURNAL OF HeErepiIrTy, VII, 
