Journal of Experimental Botany, Vol. 54, No. 381, pp. 175–178, January 2003
DOI: 10.1093/jxb/erg075
Plant culture: thirteen seasonal pieces
January – bark, the skin of a tree
Nicholas H. Battey
To a remarkable extent current science, and the attitudes of current scientists,
correspond to an idea conceived by Francis Bacon 400 years ago. Bacon
dreamed of using science to subjugate nature for mankind. This is illustrated
here by a science-eye’s view of bark, a feature of plants particularly apparent in
January. But much of the beauty and value of plants is missed by Baconian
analysis. The touching story of Daphne’s metamorphosis into a laurel, her skin
becoming bark, shows one such dimension, highlighted in the sculpture by
Bernini.
The Student’s Prayer
‘To God the Father, God the Word, God the Spirit, we pour
out our humble and burning prayers, that mindful of the
miseries of the human race and this our mortal pilgrimage in
which we wear out evil days and few, they would send
down upon us new streams from the fountains of their
mercy for the relief of our distress: and this too we would
ask, that our human interests may not stand in the way of
the divine, nor from the unlocking of the paths of sense and
the enkindling of a greater light in nature may any unbelief
or darkness arise in our minds to shut out the knowledge of
the divine mysteries; but rather that the intellect made clean
and pure from all vain fancies, and subjecting itself in
voluntary submission to the divine oracles, may render to
faith the things that belong to faith.’
Francis Bacon (~1602)
Francis Bacon was born on 22 January 1561. His great hope was set out in
his Student’s Prayer, quoted above. This prefaced a work unpublished in his
lifetime and named ‘The Masculine Birth of Time: the Great Restoration of
the Power of Man over the Universe’; it eventually appeared in altered form
in 1620, as The Great Instauration. Bacon’s big idea was of science as a
practical means to improve the lot of mankind, by domination and
exploitation of nature. He passionately criticized existing science and
ancient philosophy for describing the natural world without sufficient
consideration of mechanism.
Journal of Experimental Biology, Vol. 54, No. 381, © Society for Experimental Biology 2003; all rights reserved
176 Battey
As the first great articulator of the project of modern science, it is
interesting to see the extent to which Bacon’s ideas are still reflected in the
character of scientists and science. He emphasized the need to clear the
mind of false ideas, particularly those associated with too much booklearning, and insisted on active observation as the only means to generate a
useful Natural History. And he anticipated the notion of ascetic selfpurification, in which the body as well as the mind needs to be made pure
and ready for its work as an instrument for objective analysis of the world.
The keeping of journals, weather-diaries, a strict daily regimen and diet, all
were important methods used by scientists in the subsequent centuries to
achieve the required purity, and to detect the sinister, potentially
subjectivizing influences of the passions.
Case study: a Baconian view of bark
Bacon is associated with January by his birth date. In The White Goddess
Robert Graves mythologically links the birch tree to January; birch is also
related in meaning to bark, presumably because of the importance of birch
bark to early man. For deciduous trees of northern temperate regions bark
stands out in January, and like the Roman god Janus, for whom January is
named, these faces of trees look all ways at once. What would a scientist,
inheritor of the tradition of Francis Bacon, say about bark? Acceptable
questions would relate to useful, exploitable outcomes: origins, functions,
past and present use to man, areas for future research.
‘Bark’ describes all the tissues outside the
vascular cambium, and includes epidermis,
cortex and phloem (Fig. 1A). These primary
tissues can provide a thin bark on their own, in
laurel (Laurus nobilis), for example. The
secondary tissues that generate the bark of
most trees, however, arise somewhere within
these primary tissues, and are derived from the
cork cambium (phellogen). The phellogen
gives rise outwards to the phellem and inwards
to the phelloderm, the three tissues together
making up the periderm. The relationships
and spatial distributions of these tissues are
summarized in Fig. 1B.
The distinctive character of different barks
reflects the extent of periderm formation, and
the way in which successive periderms arise, in
conjunction with the pattern of phloem
element distribution. In smooth-barked beech
(Fagus sylvatica) and hornbeam (Carpinus
betulus) (Fig. 2A) the periderm arises
superficially and remains there, the cells
dividing and enlarging to accommodate the
Fig. 1. (A, B) What bark is
and where it comes from: E,
epidermis; C, cortex; P,
phloem; X, xylem; VC,
vascular cambium. (Based
on Eames and MacDaniel,
1925. Drawings courtesy of
Steven Appleby.)
Plant culture: January 177
increase in tree girth with age. Birch (Betula spp.) (Fig. 2B) is similar, but
the bark tears off in sheets through thin-walled phellem cells produced by
the phellogen. Scaly, furrowed and ring barks (Fig. 2C–F) indicate a
succession of periderms. Each new periderm arises underneath the previous
one, deeper and deeper within the living tissues of the cortex, until
eventually they form in the outer phloem. The cells of the phellem are dead
at maturity, suberized and water-resistant, so all cells outside them die.
Fig. 2. Six barks. (A) Beech
(Fagus sylvatica), smooth.
(B) Silver birch (Betula
pendula), smooth and
peeling. (C) Scots pine
(Pinus sylvestris), scaly and
rugged. (D) London plane
(Platanus × hispanica), scaly
but soft. (E) Turkey oak
(Quercus cerris), furrowed
and frowning. (F) Grapevine
(Vitis vinifera), ring bark:
shaggy.
A
B
C
D
E
F
Further detailed knowledge of the factors that drive exfoliation of bark not
only accounts for the patterns seen, but has also allowed the development of
technologies for its exploitation. Man uses bark as paper, cloth, cork, a
source of medicines, in tanning, and even, insultingly, as mulch. The tough,
semi-transparent bark of Prunus serrula (birch-bark cherry) has excited the
interest of materials scientists: it becomes stronger as it is stretched in the
direction parallel to the long axis of the cells, around the tree trunk.
This is what Bacon hoped for in The Student’s Prayer: we have ‘unlocked
the paths of sense and enkindled a greater light in nature’ for the
betterment of mankind. But we all lose something with a purely scientific
analysis of nature. Depth and value to our understanding of plants are
178 Battey
added from many other, often unlikely sources. Take the story
of Daphne and Apollo in Ovid’s Metamorphoses. Apollo is
smitten with love for the young nymph Daphne, desiring to
marry her: ‘his whole heart was aflame, and he nourished his
fruitless hope on love’. To escape Apollo’s clutches, Daphne
cries for help to her father, the river god Peneus. Her wish is
granted, but by means of her cruel transformation into a laurel.
In Bernini’s sculpting of the couple at the moment of this
metamorphosis, the poignancy of the tale is captured by two
principal elements: the expression on Daphne’s face, fear at
being caught becoming horror as she realizes her fate; and
Apollo’s surprise as his hand touches the surface of a tree,
instead of Daphne (Fig. 3). The sculpture makes this real
through its three-dimensional sense of touching: not flesh, but
bark. Useless to Bacon and unscientific, but a timeless allegory
on the impossibility of ownership in love.
Bibliography
Bolland A. 2000. Desiderio and diletto: vision, touch, and the
poetics of Bernini’s Apollo and Daphne. The Art Bulletin 82, 309-330.
Borger GA. 1973. Development and shedding of bark. In: Kozlowski TT,
ed. Shedding of plant parts. New York, London: Academic Press, 205-236.
Eames AJ, MacDaniel LH. 1925. An introduction to plant anatomy. New
York: McGraw-Hill.
Farrington B. 1964. The philosophy of Francis Bacon. Liverpool University
Press.
Golinski J. 2002. The care of the self and the masculine birth of science.
History of Science 40, 125-145.
Graves R. 1948. The white goddess: a historical grammar of poetic myth.
London: Faber&Faber.
The metamorphoses of Ovid. Translated and with an introduction by Mary M
Innes, 1955. Middlesex: Penguin.
Xu X, Schneider E, Chien AT, Wudl F. 1997. Nature’s high-strength
semitransparent film: the remarkable mechanical properties of Prunus
serrula bark. Chemistry of Materials 9, 1906-1908.
Fig. 3. Bernini’s Apollo and
Daphne (Photo Scala,
Florence).
The author
Nicholas H. Battey
Plant Science Laboratories, The University of Reading, Whiteknights, Reading
RG6 6AS, UK
Fax: +44 (0)118 3788160. E-mail: [email protected]
Plant culture: thirteen seasonal pieces