lie 
JOURNAL OF HORTICULTURE AND COTTAGE GARDENER. 
[ August 7, 1890. 
Ill-elaborated sap has its outcome iu eruptions, culminating in 
shrinkage or decay of the affected part. 
Canker, when it attacks Apple or Pear trees, marks its advent 
by the enlargement of the bark, whether it be of a branch or 
of the stem. There is invariably a swelling more pronounced in 
the Apple than the Pear, yet always present in those trees, and in 
neither case accompanied by a material discharge. Beyond the 
mere unnatural enlargement there is no trace or marks of disease, 
but the swelling increases, influenced by the favourable or un¬ 
favourable conditions under which the tree is vegetating; the 
alburnum dies, the bark cracks, rises in discoloured scales, and 
-decay rapidly ensues. Small branches are soon encircled by the 
decay, extending through the whole alburnum and bark ; moderate 
sized and large branches, even the stem itself, fall a prey to the 
evil, until ultimately the circulation of the sap is prevented, and 
the wood above the diseased part perishes. 
In the Apple and Pear the true sap contains a considerable 
quantity of free acid, and in this there is, when the energy 
becomes impaired, a marked tendency to secrete the calcareous 
saline compounds, and though there is no discharge, as in the case 
-of the Oak and Elm, there is a great destruction of wood. In the 
•Oak and Elm, the sap of which is characterised by abounding in 
astringent or mucilaginous constituents, the discharge is copious, 
particularly in the Elm. I have seen this morbid product flow 
from the stem of a tree so copiously as to saturate the ground to a 
considerable extent around, attracting a number of wasps. On the 
edges of the canker in Apple trees Sir H. Davy found carbonate of 
lime, the bark over which the matter flows in the Elm attains the 
appearance of chalk, effervescing with acids. A blackish varnish¬ 
like deposit is left on the bark of the Elm, not infrequently hang¬ 
ing like stalactites, the matter being alkaline, and effervescent with 
acids. The white matter formed round the edges of the canker is 
composed, according to Yauquelin, of carbonate of potass, 34'2 per 
cent. ; carbonate of lime, 5 ; carbonate of magnesia, 03 ; and 
vegetable matter, GO 5. 
That the discharge is highly destructive of the wood is apparent, 
yet the destruction is not so great as the observer may conclude, as 
the amount of saline constituents in the healthy sap are largely and 
unnaturally increased in the diseased state. When the sap be¬ 
comes vitiated—unnaturally saline—the tree becomes debilitated, 
and loses its power of selecting by its roots congenial nourishment. 
■Canker, then, arises from a tendency to secrete calcareous saline 
compounds, due to acids prevailing over the alkalies. The remedy 
is easy—supply more alkali and the acid will be neutralised. 
Excessive moisture in soils induces succulent growth, weakness, and 
early decay. Draining is the prime agent by which the super¬ 
abundant moisture is removed, the food of plants being destroyed 
by its presence, and as we remove the cause so will the roots 
recover their sensitiveness by the increase of temperature that follows 
the draining. Then it is a property of iron to sink, so by taking 
away the superabundant water we draw off a considerable portion 
of the iron. Still there are acids which have been formed, and we 
can only get rid of them by a neutralising agent. In this case 
>quick (hydrate of) lime w T ill afford what is required as a corrective. 
That, however, is not enough. Soils that have formed a pan must 
Tiave it broken up by trenching and due exposure to the atmosphere, 
so as to affect their amelioration. Six tons of quicklime per acre 
will mostly be sufficient to correct the acidity of soils. Want of 
moisture in soils may be palliated by a dressing of chalk, the 
acids being neutralised by it in light soil, as they are by the quick¬ 
lime in heavy and wet land, and in proportion as the neutralisation 
goes on so is the ammonia liberated from the iron. A dressing of clay 
marl would be even more advantageous, as its lime has the ad¬ 
ditional benefit of alumina, which with iron has the property of 
attracting ammonia. If the soil rest on irony gravel this must 
be removed, and an artificial drainage of chalk substituted, or in 
case of a subsoil not necessarily gravelly, but in which iron largely 
..abounds, it may be necessary to put in concrete to prevent the roots 
passing into the unfavourable irony subsoil. The debris of an 
old building—the lime or old mortar rubbish freed of old laths— 
15 to 9 inches thick answer well on retentive soils, and a similar 
thickness of chalk where the soil is light. 
Soil, however, is not everything. If the roots are deep they 
■will send up colder and cruder food ; if shallow they may afford a 
-meagre and uncertain supply. When a few strong roots run riot 
in a loose rich soil the growths are gorged with sap and liable to 
injury by frost, resulting in canker. This can be rectified by 
lifting and replanting in firmer soil. The over-vigorous tree will 
have much wood but proportionately few leaves before lifting, 
-afterwards not nearly so much wood but many more leaves, which 
means improved digestion, more perfectly elaborated sap, higher 
assimilation, and a greater store of ripened wood. This makes the 
^difference between the unhealthy and healthy, between the unfruit¬ 
ful and fruitful, tree. 
Canker may also be induced by severe or injudicious pruning' 
The removal of large branches late in spring is prejudicial. When 
recourse is had to severe pruning, especially of old trees, it should 
always be practised when they are in full leaf, and after the 
sun has passed the meridian, so that the growths retained may 
have the benefit of the remaining part of the year’s light and 
warmth to mature the wood and store up food for the coming 
season. Late pruning is also bad, especially for luxuriant trees, as 
it tends to late growths, which are liable to be damaged in severe 
winters. Where growth is so superabundant as to necessitate 
severe pruning two palliatives only will avail—-viz., root-pruning, 
or allowing the branches more space for extension. A tender 
variety is more subject to canker than a hardy one. That points 
to the necessity of selection—preserving and propagating from the 
most suitable. There is the question of bruises and the punctures 
of insects causing canker. I have never known a bruise result in 
canker, and though the bark may be punctured or the wood drilled 
by insects, no canker, so far as I have observed, could be traced 
thereto.— Gf. Abbey. 
PARISIAN HORTICULTURE. 
The rush and bustle of the show season during the past 
two months have interrupted my Parisian notes, and several little 
chapters have yet to be written. Before, however, the present 
contribution reaches the hands of Journal readers I expect to 
be in 'reland amongst the gardens and gardeners of our sister 
isle. Numerous kindly invitations, a full programme, and an 
earnest desire to see everything worthy of record, will occupy 
my time there, consequently I have taken advantage of this 
opportunity to refer to one of the most pleasant of my Parisian 
excursions. 
Starting from the Hotel de Londres, near the St. Lazare 
station, Baron Adolphe de Rothschild’s residence in the Rue 
M n?eau was first visited to obtain the necessary permission, 
most readily accorded, to visit the demesne at Boulogne sur 
Seine, the special object of the day’s journey. A short time was 
then spent in the charming Parc Mon^eau, a perfect little 
model of what a town park should be, and to which 1 hope to 
refer again at the first opportunity. Thence proceeding by 
road to the Champs Elysee, a drive by way of the Arc de 
Triomphe and the Place de l’Etoile was commenced of a most 
enjoyable character on a brilliant sunny day such as have been 
too rare this season. 
The Bois de Boulogne. 
The praises of this delightful resort have been frequently 
sung in the pages of this Journal, and no visitor familiar with 
our too formal London drives and parks could fail to be im¬ 
pressed with the scenery in the Bois. We have nothing like it in 
London or even in England as a public park. With regard to 
extent alone, I believe Richmond Park most nearly approaches 
it, with somewhat the advantage by a few acres, the “ Bois ” 
covering about 2000 acres. But there is no further similarity 
between the two parks, except that they are both well wooded, 
though again Richmond has the advantage in the size of its 
“specimen” trees, and in the “ Bois ” there are comparatively 
few of an unusual character. As a portion of an old forest it has 
included many fine trees, and the remains of some may still be 
found that in various troublous times have been destroyed, 
either wantonly, by accident, or for use in several ways. The 
“ original ” forest was largely composed of Quercus sessiliflora, 
the Chene rouvre of the older French writers, and there are 
numbers of this Oak in the present “ Bois,” but many other trees 
have been largely planted, with the result that the diversity of 
aspect has been advantageously increased. The denseness of 
the tree and shrub growth has been a great help in improving 
the picturesque appearance of the “ Bois,” for jud’eious cutting 
and clearing have in some instances effected much more than 
could have been accomplished by planting or artificial design. 
It is probable, too, that still further improvement would result 
from an extension of the clearing process at suitable points. 
Observers have remarked a want of breadth as being the chief 
defect of the place, and this is true; but it must be remembered 
that the actual width of the park, if it may be so termed, is 
small compared with its length, and it would be difficult to secure 
an open space of sufficient extent to justify the wholesale 
sacrifice of the present occupants. In Hyde Park and Richmond 
Park, already mentioned, we have these grand open breezy 
spaces to perfection, and the breadth of the parks themselves 
admits of this without detracting from their general beauty. 
The drives through the Bois de Boulogne are the special 
features, because, like the avenues and boulevards of Paris, they 
are spacious, tree-shaded, and well watered and kept. Extending 
