October 9, 1890. J 
JOURNAL OF HORTICULTURE AND COTTAGE GARDENER. 
321 
much in the position of some of our modern houses of business, 
which during the season put forth branches at the various watering 
places, and do a thriving trade ; but when winter drives custom away 
they find it pay best to withdraw their “ staff ” and stock, and close 
until the next season. It is no less plain that if all leaves remained in 
situ through the winter the balance of profit would turn against the 
parent tree instead of for it. Those which, during summer’s sunshine, 
are the great source whence the tree draws its supplies and grows there¬ 
by would have themselves to be supplied whilst winter’s cold prevailed. 
The cost of such nourishment and repair through the cold dark months 
would have to be subtracted from the proceeds of summer work. The 
tree would be by this so much the loser that plain principles of economy, 
working in nature according to the law of each organism’s being, not by 
caprice as in human nature, demand their removal. 
(2) But even this called-for removal is done economically. As the 
business firm which closes its season shops takes good care first to 
remove all valuables, so before the leaves are dropped off their respec¬ 
tive branches, they are previously drained of their precious contents by 
processes which collect, transform, and transport them into persistent 
reserves in the parent organism. Thus, when winter once more melts 
into spring, and the vital mysteries of spring energy begin to express 
themselves in renewed growth, there are materials at hand to work upon, 
so that forces from within and from below may combine to produce the 
new buds whence are to come the twigs, branches, and leaves for another 
season’s ingathering. 
To describe in detail the draining processes referred to would require 
no little space. It must suffice here to note that it varies in different 
trees. In the Vine the form of the chlorophyll corpuscles is first de¬ 
stroyed, then the colour goes. In the Elder and Poplar the form and 
colour of these minute bodies melt away together after the earlier dis¬ 
appearance of the starch. In the Horse Chestnut all seem to go about 
the same time. The main point to be observed is that there is a definite 
emptying by means of colliquative changes in the chlorophyll bodies. 
And it is to these changes, with their results, that the well known hues 
and tints of autumn are due. Thus (i.) in place of the real green and 
definite form of the chlorophyll corpuscle there are found in autumn 
leaves before they fall numbers of yellow oil drops, with still larger 
quantities of very small yellow granules. Their colour and substance 
are quite distinct from the etiolin which precedes the appearance of 
chlorophyll. They are, moreover, often embedded in red sap, whence 
arises the beautiful colouring which some leaves exhibit, (ii.) The 
means by which this economic work is done will be easily apprehended 
by all who bear in mind what is known as the fibro-vascular system. 
This is far too complicated to admit of detailed description here. Any 
good book upon botany, moreover— e.g ., Prantl and Vines—will supply 
the requisite information. Perhaps the best possible illustration of this 
system is found in those specimens of the “ veins ” of leaves, which are 
often obtained by maceration of the softer parts. These so-called veins 
when examined microscopically exhibit a series of tubes and vessels, 
the function of which is exceedingly difficult to define in detail, but 
which amply suffice to afford channels whereby food materials may be 
transported. It is not needful, therefore, to step aside here and decide 
the mixed puzzles of histology and biology. That (iii.) the emptying 
process referied to does take place can be shown to conviction in several 
ways. First, by micro-chemical testing, which shows that in the just 
fallen leaf there is scarcely a trace of starch, whereas the vigorous leaf 
abounds with it. Or, again, it may be demonstrated by testing carefully 
the chemical constituents of the ash of a leaf in full vigour, as com¬ 
pared with that of one naturally fallen. The presence in the former 
and absence in the latter of potash and phosphates is manifest and 
sufficient. 
(3) . The drained leaf-skeletons being then obviously of no service to 
the parent organism during the following six months, it is highly de¬ 
sirable that such should be removed. And in considering how this 
comes to pass, we aTe brought face to face with another of those marvels 
of anticipation in Nature which so deservingly astound us, and land us 
ultimately in life mysteries which laugh at all our theories of biology. 
What, for instance, do we know of the processes whereby, in the dark 
and under water, the eyes of Libellula are fashioned, with their 24,000 
facets 1 We can only say, with Topsy, that we suppose they grow. And 
it is a no less remarkable work of Nature which underlies by anticipa¬ 
tion the autumnal leaf-fail. 
Long before the leaf shows any signs of dissolution there are internal 
indications of a coming change. These consist in the development of 
two new cortical features at the base of the petiole—viz., periderm and 
the absciss layer. The latter is a layer of special cells— smaller, more 
rounded, and more loosely coherent than the ordinary cortical paren¬ 
chyma—which is formed immediately beneath the base of the leafstalk. 
This is not always equally easy to make out distinctly, yet it may be 
plainly observed in the following :—.Esculus Iiippocastanum (Horse 
Chestnut), Robinia pseudacacia (Bastard Acacia), Populus dilatata. If 
access to Gymnocladus canadensis (Kentucky Coffee-tree) be possible it 
is a specially suitable subject for illustration, and may be experimented 
on. Thus if strong leaves are placed in the dark or damp an absciss 
layer is formed at once under the base of the leaflet-stalks, so that in 
about two days the leaflets drop off on the slightest touch. Almost 
equally good subjects for investigation are Ailantus glandulosa, 
Fraxinus excelsior, and Juglans regia. For ordinary students the Horse 
Chestnut is best, both because of its easy accessibility and plainness of 
demonstration. When the absciss layer is fully developed the leaf drops 
off with a very small amount of mechanical disturbance, thus especially 
through the force of the wind. 
Sachs also interestingly states how temperature effects a similar 
result. The cells of the absciss layer being loose and rounded allow of 
the presence of more water than usual in their interstices. Thus with 
the first frosty nights of October a thin plate of ice is formed as a plane 
of separation from the parent branch, underneath the base of petiole. 
The well-known expansive power of ice acts here as elsewhere, conse¬ 
quently the leaf and its stalk are gently all but severed from the tree,, 
and when the sun arises there is in its rays sufficient heat to melt the 
ice film, whence, in the morning, leaves drop off in great numbers. 
(4) But the anticipative power of Nature is still more manifest when 
we consider the means adopted for prevention of injury at the points 
left bare by the removed petiole. Ordinarily, of course, the fibro- 
vascular threads which ramify through the leaf blade are collected 
together into a string or bundle, passing down the leafstalk and joining 
others in the parent branch or tree ; but whilst the absciss layer 
immediately precedes the fall of the leafstalk there is much earlier a 
remarkable formation (on the inner side of where it afterwards appears) 
of what is known as periderm. 
To make this intelligible to non-technical readers it must be pointed 
out as tersely as possible that plants require a “ skin ” as much as 
animals. They can no more afford to have bleeding spots without a 
protecting cuticle than we ; hence they are provided with an epidermis,, 
which in all trees and large plants involves more or less of cork. 
Generally the epidermis serves three functions—(1) prevention of 
excessive evaporation ; (2) protection from injury ; (3) strengthening. 
Here we are concerned with 1 and 2. It must be remembered that what 
is properly termed cork really involves several distinct layers of cells,, 
histologically considered. The most important is a layer of actively 
dividing cells, known as phellogen or cork cambium, from which are 
formed externally cork proper or phellem, and internally phelloderm. 
The whole of these is included in the name periderm. 
Now, it is of great importance that a corky shield should protectingly 
cover up for the winter the spots which are left naked by leaf-fall ; but 
this can only be done from within. Nothing can grow out from the 
external cork to form a covering. As a matter of fact the periderm is 
formed long before leaf-fail, even whilst the fibro-vascular bundles are 
in full discharge of their functions, hence they pass right through this- 
growing plane of periderm, and their broken off ends at first project 
when the petiole is actually removed, and it is to these the peculiar 
marks are due, which are seen in every “leaf scar."’ 
When the leafstalk drops off, carrying the absciss layer with it, 
there is left behind at first apparently some greenish parenchyma cells 
on the outside ; but the foregoing section shows that under this veil of 
parenchyma there is already prepared a layer of periderm, with its plane 
extending beneath the whole, except through the fibro-vasal bundles ; 
but now it begins to develop through these also —that is, right across the 
roundish area left bare, consequently the outer cells just mentioned dry 
up, and ultimately a completely closed layer of cork is formed over the 
recently exposed tender spot; this increases somewhat in thickness until 
the branch is effectually protected against the coming storm and cold of 
winter, thus the tree remains adapted to its environment until once 
more spring draws on, and the daily increasing amounts of heat and 
light indicate that it is safe and profitable to put forth again buds and 
leaves. Then recommences that fixation of carbon with evolution of 
oxygen, whereby the tree itself is nourished and the healthful balance 
between the vegetable and animal world is so wondrously maintained. 
It seems to me impossible to attribute the marvellous inter-working of 
all these processes, reasonably to mere fortuity.—R ev. F. Ballard, 
M.A., B.Sc. (in The Journal of Microscopy for October , 1800.") 
Chrysanthemums in the South. 
The time is now fast approaching when growers will become anxious 
as to their chance of success at the forthcoming exhibitions ; they will 
be comparing their plants with those of their neighbours to ascertain if 
they are likely to be too early or too late, too weak or too strong, and 
so forth. Each grower has fancies of his own m these respects ; and as 
everyone has not the opportunity of inspecting for themselves the 
collections of plants belonging to exhibitors in the past, and would still 
like to know how their probable opponents-are “ looking”—a familiar 
term amongst growers of Chrysanthemums—I will note what I saw in a 
hurried run through some gardens a short time since. 
Messrs. W. & G. Drover’s nursery at Fareham, during the last few years 
especially, have devoted much attention to Chrysanthemums for large 
blooms, and with excellent results. Many new varieties have been tested 
to discover their worth for exhibition. The greater part of the space in 
the nursery is covered with glass houses devoted to the flower trade. 
The plants are arranged in blocks, the lines running north and south 
parallel with the glass structures, and one very long row of Japanese 
is arranged in front of a lean-to range of houses on the edge of the path. 
