May 1, 1890. ] 
JOURNAL OF HORTICULTURE AND COTTAGE GARDENER. 
355 
^vill derive little benefit from the screen trees until they have 
arrived at or passed the meridian of their profitable period. Nor is 
this all, for where no natural shelter exists it is a question whether 
forming artificial shelter will not so detract from the results as to 
render the affair unprofitable. This is a matter for serious con- 
•sideration. It is one thing to have a slope of ten, twenty, or more 
acres with the shelter above indicated, for which there is no rent to 
pay, and having shelter to provide on ground that is rented equally 
with that occupied wiih fruit trees ; indeed it is a moot question 
whether ground not already sheltered should not be rejected, or if 
sheltered at all, it ought to yield a profitable return for the ground 
on which rent has to be paid. The landlord might, of course, sre 
that by planting the ground undesired by the fruit grower with 
forest trees, the fruit growing portion would be rendered more 
valuable, and bring a higher rental, such as would compensate him 
for the loss that must accrue on outlay in planting and loss of rent 
until the plantation came into profit, but unless the land was un¬ 
suitable for arable or grazing purposes it is problematical, if he 
would fall in with such a plan for seeking profit by letting land for 
fruit growing. Clearly any expense incurred in sheltering would 
have to be borne by the person for w'hose benefit it was provided, 
and to recoup that it must be profitable. 
The progress made by vegetation on southern exposures requires 
protection so as to moderate the effects of cold winds. The points 
where protection is required are on the north, north-east, and 
north-west sides, as from these the winds are the coldest, and the 
north and north-east worst of all, therefore the shelter should 
approach nearest on those sides, for what is lost in light will be 
compensated in warmth, and the north-west, though it may be less 
important, should not be much further removed. On the east and 
west sides the shelter should be at such distance as not to deprive 
the site of the morning and evening sun. On the north and north¬ 
east the screen should not be nearer than 20 yards, as the sheltering 
trees to be of use muse be larger and stronger than the fruit trees, 
and the shelter must be brought round similarly on the north-west. 
On the east side the shelter should be fully double the distance off, 
as on the north, north-east, and north-west sides, and it is preferable 
to have the shelter on the east and west in copse or clump order, 
and widening out to the south-east and south-west respectively, so 
as to leave the fruit garden or orchard quite open to the south-east, 
south, and south-west. In planting in clamps it is necessary to 
liave double lines, so that the further off shall be opposite the 
inner intervals or openings. These will break the force of winds 
effectually, and letting in more light are decidedly preferable 
to an unbroken closer screen. In situations much exposed to the 
south-west it may be desirable to offer protection in the shape of 
outpost clumps, so as to break the force of wind before it reach 
the fruit trees ; but they must be a considerable distance (not 
less than 200 yards), or they may interfere with the free access 
of light, which it is imperative must be afforded unobstructed 
between east and west. In very exposed locations the outpost 
system of shelter has great advantage, as with clumps of trees 
at 200 to 300 yards distance, an outer one at the latter and an 
inner one at the first, and so that they come alternate and to 
some extent overlapping, the force of wind is so broken that it 
falls very much weaker on the inner screen and makes a consider¬ 
able difference in the temperature. In many, if not most, localities 
where suitable sites offer for fruit gardens and orchards there is 
■generally a large amount of plantation, natural or other copse, 
particularly in undulating lands, along with hedgerow timber, which 
independently of woods that collectively so break and modify the 
force of winds as to render artificial shelter unnecessary, or it may 
be neces.sary to fell some of the existing trees so as to let in more 
of the forenoon and afternoon sun. This, however, can only be 
■determined by ocular proof on the spot, and requires to be done 
with consummate judgment and knowledge of the locality. 
Tall and quick growing trees should be chosen. None excels in 
ihese aspects the Larch, Corsican Pine and Scotch Fir, with the 
Austrian Pine for the outer and inner lines of the belt, as the 
Austrian Pine is very dense in growth and does not become so bare 
at the bottom after a few years as the other. These answer 
admirably on the north, north-cast and north-west, and will thrive 
r.t elevations and on ground where quick growing deciduous trees 
could not. Poplars and Limes are much employed for shelter of 
this kind, to which there is no objection if the site be in a level 
country or where there is plenty of moisture with a good depth 
of soil, but they are not suitable for sheltering on high ground 
where the soil may ba too poor from elevation, although the site 
to be sheltered may possess a good depth of rich soil through the 
washing down of the finer and richer parts from the higher ground. 
1 he belt should not be less than nine rows deep, the centre one 
■Corsican Pine alternate with Larch, next Larch entirely, then Scotch 
F ir, every other plant Lirch, another entire row of Larch, anl an 
•outside one of Austrian Pine alternating with Larch, repea'ing the 
lines on the other side of the line of Corsicin Pine. In the lines of 
Scotch Fir introduce Elm and Sycamore, or Beech if chalky, at every 
IG feet, and at similar distance in the lines of Austrian Pine Moun¬ 
tain Ash may bo planted, but Holly is preferable on the inner line. 
This belt would be profitable from the thinnings after a few years, 
and being planted 4 feet apart the trees would get up quickly, so 
that by the time the orchard or fruit garden was in full profit it 
would be materially augmented by the timber, indeed, it is ques¬ 
tionable which of the two would upon the capital afford the best 
results. On low and damp soil Poplars would be most suitable, 
the Black Italian perhaps best, and for evergreen Norway Spruce 
might answer if not too much exposed, otherwise it is about one of 
the worst sheltering trees. For soils of medium texture Limes do 
very well, but they are useless in heavy clay soils, though they 
thrive well enough in moist and light, and they may be trained and 
cut so as to form a close screen from the ground upwards. It is 
certain that if we need screens of the deciduous character and have 
to pay rent or own the ground on which they stand, that it would 
be more rational to plant sheltering belts of the stronger freer 
growing kinds of Apples or Pears (and Damsons or hardier kinds 
of Plums for dwarf culture), for it is patent that if the S9il is good 
enough for a Poplar, a Sycamore, or a Lime, which have little va'ue 
as timber, it will grow equally free examples in fruit trees. There¬ 
fore if shelter is provided in such cases it will only need to be of 
a temporary nature, and the trees should be planted closely so as 
to grow quickly, for which there is nothing better than Poplars 
and Willows. Where but a low screen is wanted, as in the case of 
trees under dwarf culture, nothing surpasses the common Elder, 
and it will stand sea breezes, evidently relishing the salty air. To 
enable the screening trees to advance quickly, the ground should be 
well trenched and liberally manured, keeping it free of weeds so 
as to let them have full possession of the soil.—G. Abbey. 
(To be o.n'inued.) 
VARIATION IN PLANTS. 
(^Contimicd from 2 )aje 335.) 
Natural Adaptations Favouring Cross-fertilis.vtion. 
What is commonly unders'iood by the term cross-fertilisation or 
hybridisation is the transference of the pollen of one plant to the 
flower of another, and though in garden nomenclature a distinction 
is made between the two terms, no such distinction can occur in 
regard to wild plants. The fertilisation of one species by another 
we term hybridisation ; and crossing, cross-breeding, or cross-ter- 
tilisation is usually restricted to the same process between varieties 
of one species. It is mors convenient to employ cross-fertilisation 
in its broadest signification, and there are so many different grades 
of fertilisation, that it is not desirable to attempt a division of the 
subject by the use of terms so nearly synonymous. 
For example, self-fertilisation pure and simple takes place when 
a flower is fertilised by pollen from its own anthers ; if pollen from 
another flower on the same stem or plant is employed, we have the 
first form of cross-fertilisation, and the results may be quite dif¬ 
ferent from those in the first named case. 
The next grade is when the flower of a plant is fertilised with 
pollen from another plant growing in the same soil and situation, 
and of the same variety or species. The third grade is the fertilisa¬ 
tion of a flower with pollen from the same species or variety, but 
furnished by a plant growing some distance away and under dif¬ 
ferent conditions. Within the limit of one variety we thus have 
three degrees of cross-fertilisation, and it has been proved re¬ 
peatedly that the benefit in greater fertility, better seeds, or stronger 
seedlings, usually increases with the divergence of one parent from 
the other. Thus there turns are least in the self-fertilised flower. An 
advantage is gained in the case of fertilisation by pollen from 
another flower on the same plant ; this is increased when the po'len 
is from another plant, and still more when the plant is grown else¬ 
where, provided in every case they be equally healthy. 
Following the grades already named, we have cross-fertilisation 
of one variety by another m the same species, then between two 
species in one genus, and lastly between two species of different 
genera. These six degrees represent the whole range of the com¬ 
binations that can be distinguished, though there are other minor 
differences that have an effect though they may not always be 
immediately appreciable. For instance, the plants raised from a 
self-fertilised seed-pod might be regarded as more nearly related 
than any others, but there would be a slight difference between 
them and those from other seed pods on the same or different 
plants, and so or. 
It is beyond all question that with many plants cross fertilisa¬ 
tion is a distinct advantage, and the fact that some plants are 
liabitually self-fertilised in a wild state does not in any way dis- 
