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53
Botanical Lessons
Plant organisation (1/2)
Leaves of the family Crassulaceae (here the
example of the houseleek, Sempervivum
montanum) can store water as an adaptation
to drought
Flowering plants are composed of three parts: roots, stems and leaves.
Potatoes are stems that have been modified to
store nutrient reserves. In common with all stems,
they carry the buds ("eyes")
blade
veins
Roots. Most often found underground, roots anchor plants to the soil and absorb water and mineral
elements required for growth. They can be either taproots (a single vertical root) or fasciculate.
Sometimes roots also store reserves (such as in the carrot).
The stem. Generally found aboveground, stems carry the buds, which determine the growth,
ramification and flowering of the plant. Stems maintain the plant upright and are essential for the
petiole
stipules
alternate
opposite
General organisation of a leaf and examples of
the arrangements "alternate" and "opposite"
transport of nutrients (sap). Stems can be herbaceous, or rigid and lignified (wood) in shrubs and trees.
Diagram of a plant: roots (in black, here
fasciculate, with numerous roots attached to
the same point), stem (in brown), leaves (in
green) and a flower (in blue). The stolons are
above ground stems which grow horizontally
and produce clones of the mother plant.
Leaves. Leaves are the principal organ of photosynthesis and transpiration. They generally
comprise of two parts: the lamina and the petiole. The lamina is a flattened blade containing veins
lanceolate ovate
obovate
orbicular
sagittate
pennatilobate cordate
which transport the sap. The shape, margin and pattern of veins differ between species and
constitute criteria for identification. The lamina is divided into leaflets, in the case of leaves called
pedate
“compound” leaves. The petiole, which is sometimes absent, attaches the leaf to the stem.
Phyllotaxy describes the arrangement of leaves on the stem. Leaves can, for example, be grouped
An example of a plant with both an
underground stem, or rhizome (in brown), and
an above ground stem; the roots (in black) are
called “adventive” (newly formed on the stem)
in pairs attached face to face along the stem (leaves called "opposite") or be rather isolated and
arranged regularly in a spiral around the stem (leaves called "alternate").
palmate
paripennate
imparipennate
A few examples of the diversity of leaf blades. In
brown, the petiole, in dark green, some
examples of "compound" leaves
Botanical Lessons
53
Plant organisation (2/2)
Two gentians: Gentianella campestris (left,
hemicryptophyte) and Gentiana nivalis (right, a
rare alpine therophyte)
The daffodil (Narcissus poeticus,
Amaryllidaceae family), an example of a
cryptophyte plant with a bulb
The Danish botanist Christen Raunkiær (1860-1938) developed a classification of plants founded on
their strategies to survive bad winter conditions. This classification is based on the position of plant
A. Phanerophytes (trees, shrubs > 50 cm)
Perennial
plants
Annual
plants
B. Chamephytes
subshrubs (a), creeping shrubs (b), plants with woody basee (c)
C. Hemicryptophytes
rosettes (d ), tufts (e)
D. Cryptophytes (ou geophytes)
with rhizome (f ), or bulb (g)
buds during the winter. Phanerophytes are trees and shrubs higher than 50 cm. Their buds are not
protected from frost by snow cover, which is one of the reasons that trees are absent from the alpine
zone. Chamephytes are small shrubs whose buds are sufficiently low to be protected by snow cover.
Numerous cushion plants from dry mountain areas (see the rockery “Spanish mountains”) have
E. Therophytes
woody bases and also belong to this category. Hemicryptophytes have their buds located at soil
A
C
level, and their leaves form either a rosette (such as the Dandelion) or a tussock (such as in numerous
D
e
Poaceae or Cyperaceae). Cryptophytes (also called Geophytes) have their buds buried, and thus
f
B
50 cm
a
c
d
g
E
b
protected from cold under the ground (geo in Greek). The buds are situated on the rhizomes
(underground stems) or on bulbs which accumulate reserves to fuel the beginning of growth for the
next year. Therophytes are annual species. These species pass the winter period as seeds, highly
resistant to aridity and frost. Very common in arid areas, annual species are almost non-existent in
alpine areas, mostly because of the highly random nature of the possibility for sexual reproduction at
high altitudes.
The principal "biological types" based on the position of the buds during winter (in red). In black, the perennial
parts of the plant that remain from one year to the next; dotted lines, the plant parts that die during the winter.
Etymology of the terms: "phanero", visible; "chamae", dwarf; "hemi", half; "crypto", hidden; "thero", summer.
Botanical Lessons
53
The concept of the alpine plant (1/2)
The mountain avens (Dryas octopetala,
Rosaceae family), an example of an
arctic-alpine plant
The gentians (here Gentiana acaulis,
Gentianaceae family), examples of plants
originating from the Himalayan region
Altitudinal vegetation zones. Mountain vegetation is divided into zones, each with a characteristic type
of vegetation. The upper limit of the sub alpine zone marks the natural limit (without human
South
ADRET
North
2400 m
zone where environmental conditions become more and more extreme with altitude due to
decreasing mean temperatures, increasing solar radiation, strong winds, etc. The sub alpine / alpine
NIVAL belt
3000 m
intervention) of trees. This limit is found around 2300 m altitude in the Alps. Higher up is found the alpine
UBAC
mosses, lichens
2900 m
ALPINE belt
come from subalpine and alpine zones.
Etage SUBALPIN
conifer forests
Multiple origins for the flora of the Alps. The current alpine flora is the result of a colonisation begun some
10 000 years after the retreat of the glaciers. The major vegetation influences come from the
MOUNTAIN belt
mixed forests
COLLINEAN belt
broadleaved forests
Routes of the plant colonisation of the Alps: 1,
Mediterranean; 2, Central Asian; 3, Arctic
endangering those plants that grow at high altitudes. The plants growing in the Lautaret alpine garden
1500 m
1100 m
an alpine plant is a species that grows in the alpine zone, in the Alps or another mountain region.
Determined mostly by temperature, the limit of the alpine zone is rising due to global warming,
alpine meadows
2200 m
1700 m
boundary varies from 0 m altitude in polar areas, up to above 4000 m in tropical regions. For biologists,
900 m
Mediterranean, Central Asian (notably Himalayan) and arctic regions. In the case of the arctic region,
the alternation between glaciations and glacial retreat has contributed to numerous exchanges of
flora, resulting in the presence of numerous plant species, called arctic-alpine species, which are found
both in the Alps and in arctic regions.
The campanulas (here Campanula alpestris,
Campanulaceae family), a plant with a
Mediterranean origin
Botanical Lessons
53
The concept of the alpine plant (2/2)
Swiss
androsace
(Androsace
helvetica,
Primulaceae family), a cushion plant growing
amongst rocks at the Galibier pass (around 2800 m)
High altitude Dwarf willow (Salix serpyllifolia,
Salicaceae family) an example of a prostrate
plant
Morphological adaptations. A small size is very common amongst alpine plants, allowing them to
at the surface
of the cushion
Temperature(°C)
25
remain within 1 to 2 m of the ground where temperatures are less cold. It also allows plants to benefit
20
from protection by snow cover in winter, and limits the mechanical effects of the wind and snow which
15
10
can break stems and branches. Cushion plants are a well-known example of adaptation to extreme
at 2 m
from the cushion
5
conditions: the cushion functions as a heat trap as its geometric form exposes the least surface area to
0
9
external conditions, limiting both losses of heat (and water). Plant hairs are another adaptation: these
12
15
18
Hour of the day (summer)
form a screen that protects the plant from cold, dry and strong solar radiation. Root systems of alpine
The temperature difference between the
surface of a cushion plant and at two meters
height (using the example of silene acaule)
Vitamin C, micromol/mg chlorophylll
Structure of the Swiss androsace, an example of
a cushion plant with a long tap root
Physiological adaptations. Alpine plants synthesise molecules (sugars, anti-freeze proteins) which
alpine plants
protect their cell membranes from the effects of freezing. They can also maintain their cell contents in
5
4
a liquid state down to temperatures of -40°C. To counter oxidative stress imposed by excessive solar
3
lowland plants
2
radiation (light and UV), plant can accumulate anti-oxidants, in particular vitamin C. These
adaptations are the results of long periods of evolution. They are in part fixed in the genetic makeup of
1
0
plants can also exhibit adaptations, such as the presence of a long tap root in cushion plants.
1
2
3
4
5
6
Differences in the concentration of vitamin C
in three alpine plants (1, soldanella; 2, alpine
coltsfoot; 3, glacier ranunculus) and three
lowland plants (1, rye; 2, dandelion; 3,
meadow buttercup)
alpine species, and in part dependant on environmental conditions (acclimation).
Ces adaptations sont le fruit d'une longue évolution. Elles sont pour partie inscrites dans le patrimoine
génétique des espèces et pour partie conditionnées par les conditions environnementales (acclimatation).
The edelweiss (Leontopodium alpinum,
Asteraceae family), an example of a plant
covered with protective hairs
Botanical Lessons
53
Interspecific relationships (1/2)
Mont Cenis restharrow (Ononis cenisia,
Fabaceae family), an example of a plant
able to fix atmospheric nitrogen
Lousewort (Pedicularis comosa, Orobanchaceae
family), an example of a hemiparasitic plant
Plants have multiple types of relationships between each other, and with other organisms
atmospheric nitrogen
(N2)
(bacteria, animals). Here are a few examples
Symbiosis. This is a long term association between two organisms allowing each to obtain
organic nitrogen
(proteins)
root
nodules
(Rhizobium bacteria)
Diagram of the symbiosis between the
Fabaceae (Leguminaceae) and the
bacteria hosted in the nodules of their roots
reciprocal advantages. Plants such as the sainfoins, trefoils, milk-vetches, restharrows, clovers and
other plants of the family Fabacea, host in their roots (within nodules) bacteria (Rhizobium) which
roots of the
parasite
(haustorium)
can use atmospheric nitrogen. They transform this into organic nitrogen (amino acids and proteins)
water and
mineral nutrients
which can then be used by the plant. Similarly, lichens are the result of a symbiosis between a
fungus, which provides resistance to drying out, and an algae, which provides the synthesis of
host roots
Hemiparasitism
sugars by photosynthesis.
CO2
(atmospheric carbon)
sugars
(organic carbon)
O2
fungal
mycelia
unicellular
algae
Diagram of lichen with the fungal
mycelium (in brown) and the unicellular
algae (in green)
Parasitism. This is a relationship with negative consequences for one organism. In the case of
hemiparasitism (louseworts, rhinanthus, velvetbells, etc.), one plant accesses water and mineral
salts in the vessels (roots or stems) of the host plant, but remains green and able to also
photosynthesise itself. In the case of holoparasitism (such as for the broomrapes and dodder), the
parasite has lost the capacity to photosynthesise itself, and not only uses water and mineral salts
from the host, but also organic matter.
roots of the
parasite
(haustorium)
water and
mineral nutrients
+ organic matter
host roots
Holoparasitism
53
butterwort
leaf
enzymes
(proteases)
insect
Botanical Lessons
Interspecific relationships (2/2)
Facilitation: lady's mantle (Alchemilla sp)
(dissected leaves) benefits from the favourable microclimate next to a cushion of moss
campion (Silene acaulis)
Competition between Festuca paniculata
(large grasses) and other species in grasslands
at the Col du Lautaret
Carnivory. Carnivorous plants live in wet, poorly oxygenated areas which are low in nitrogen, which is required for the synthesis of amino
acids and proteins. The solution found by these plants consists of trapping insects within their leaves (Butterworts and Droseras have sticky
leaves) which are then digested by enzymes produced by the leaves. The amino acids that are liberated are then absorbed by the
leaves and are used in the synthesis of proteins by the plant.
organic nitrogen
(amino acids)
An insect digested by the sticky leaves of the
butterwort Pinguicula vulgaris
(Lentibulariaceae family)
Competition and facilitation. these are relationships which are not essential to the survival of one of the partners such as in the case of
parasitism or symbiosis. These types of relationships affect the growth of plants either negatively (competition) or positively (facilitation).
In the case of competition, plants compete for light
Competition
Facilitation
No interaction
the plant grows less well
with neighbours
the plant grows better
with neighbours
the plant grows in the same
manner with or without
neighbours
and mineral nutrients, which reduces the growth of less
competitive species. In the case of facilitation, one
plant benefits from the environment created by
another
plant
which
favourably
modifies
the
microclimate (protection from cold, aridity, excessive
solar radiation, etc.).
Plant with neighbouring vegetation
Plant without neighbouring vegetation (Neighbour removal)
Diagram showing three types of interactions that can exist between plant species: when plants neighbours are experimentally removed, the plant can either grow better,
less well, or in the same manner, which indicates the types of interactions that are occurring between the plant and its neighbours
Botanical Lessons
53
Plant distributions (1/2)
Saxifraga bryoides (mossy saxifrage), grows only
amongst acid siliceous rocks of the Alps and
some other European mountain areas
Saxifraga caesia (Mount Cenis saxifrage), grows
only amongst alkaline limestone rocks of the
Alps and some other European mountain areas
Some aspects of the distribution of alpine plants are presented here using the example of the
genus Saxifraga (Saxifragaceae family). This genus comprises of more than 400 species, essentially
found in the mountains of the temperate and arctic northern hemisphere, with many species found
in the Alps.
Some species, called arctic-alpine, such as Saxifraga oppositifolia or S. aizoides, have a broad
distribution in the arctic region, in the Alps and other European mountains (1). Initially distributed in
the arctic, these species migrated towards the south during the period of glaciation. As the glaciers
1. Distribution of Saxifraga oppositifolia in
Europe, an arctic –alpine species. During the
glacial period, it grew in rocky ice free areas
retreated, these species recolonized the arctic as well as the higher areas of the Alps.
2. The distribution of the two species Saxifraga
caesia and Saxifraga bryoides, two plants
found in the Alps and in other mountain regions
Other species are not present in the arctic region. Saxifraga caesia and S. bryoides (2) are two
species with a broad distribution in the Alps and some other mountain massifs. Despite their similar
distribution, the two species are not found together as they have different requirements as to the type
of areas they grow in, one grows in limestone areas (S. caesia) and the other on silicates (S. bryoides).
This is called ecological vicariance. Other species such as Saxifraga biflora only grow in the Alps
(endemic species, 3). However, it should be noted that this species also grows on a mountain in
Saxifraga oppositifolia, pink flowers)
Saxifraga biflora, white flowers)
and
Greece, maybe transported by birds, or maybe as an indicator that previously the species had a
much larger distribution (relictual species).temps où l'espèce avait une distribution plus large.
3. The distribution of Saxifraga biflora, a species
which grows only in the Alps (and on Mount
Olympus in Greece)
53
Botanical Lessons
S. hostii
S. valdensis
Plant distributions (2/2)
S. cochlearis
Saxifraga valdensis, a protected species that
grows in France only in a few locations in the
Queyras massif
Distribution of Saxifraga valdensis (westernAlps),
S. hostii (eastern Alps) et S. cochlearis
(ssouthern Alps)
The species presented here correspond to three species whose ecological requirements
are similar (plants growing in alpine zone rocky areas), but they are found in distinct
geographical areas: the eastern Alps in the case of S. hostii; the Maritime Alps for S.
cochlearis and the western Alps between France and Italy for S. valdensis. This is a case
of geographical vicariance.
In the case of the species shown opposite, scientific research has allowed for an
understanding of how these distributions developed. These species (as well as others not
shown on the map) are all descended form an ancestral species, Saxifraga cespitosa,
which is still found today in arctic regions. During the glacial period, this species migrated
towards the south. With the retreat of the glaciers, this species recolonized the arctic areas
and also most of the mountains of southern Europe. Within each of these mountain
regions, geographical isolation allowed for the divergent evolution of this original species,
and for the development of a series of endemic species. A number of these endemic
species can be found in this rockery, in the Pyrenees rockery (S. hariotii) or in the "Massif
central" rockery (S. cebennensis).
Botanical Lessons
53
Sexual reproduction
Flowers of the vernalgrass (Anthoxanthum
odoratum, Poaceae family), an example of
a plant pollinated by the wind
Two insect pollinated plants with very colourful
flowers (Peacock-eye pink and the common
rock-rose)
The flower is the central element of sexual reproduction in plants. The flower is the central element of
petal
sexual reproduction in plants. It comprises of the fertile parts: stamens (male organs) and carpel (female
organs), and the sterile parts: petals and sepals. The majority of flowers are hermaphrodites, having both
anther
filet stamen
sepal
style
ovary
ovule
pistil
male and female organs. They can be isolated, or grouped in inflorescences. The stamens are formed of
an axis (stalk) supporting at its extremity an anther, often yellow, which contains the pollen grains. The
carpel consists of an ovary containing the ovules, and one or more styles that end in a stigma, which
peduncle
The different parts of a flower, shown here for the
alpine flax (Linum alpinum, Linaceae family)
receives the pollen. Pollen is transported by different vectors. Most often, it is insects that transport pollen,
spike
capitulum
corymb
raceme
umbel
and in this case the evolution of flowers has resulted in the development of attractive features such as
bright colours, scents, particular forms or sugary nectars. In other cases, it is the wind that transports pollen,
and the flowers have no petals and no colour (for example in the Poaceae or the Cyperaceae).
Once on the stigma, a pollen grain will fertilise an ovule, which will ultimately become a seed, within a
pistil that transforms into a fruit. The fruit aids in the dispersal of the seed by the wind, by animals, by water,
etc. At high altitude, flowers often have intense colours or flower for longer, to compensate for the rarity
of insect pollinators. Many species also reproduce asexually (clonally) or through apomixis (the
An example of a compound umbel, typical
of the Apiaceae family (Umbelliferae), shown
here for the common hogweed (Heracleum
sphondylium)
production of seeds and fruits without fertilisation, such as found in the Hawkweeeds.
panicle
composed
umbel
thyrse
The principal types of inflorescences
(location of flowers on a stem). The arrows
indicate the progression of flowering of the
flowers shown in red
53
Botanical Lessons
Clonal reproduction (asexual)
The stolons of the creeping avens (Geum
reptans, Rosaceae) allow the plant to
colonise schist scree slopes
Clonal reproduction allows the violet fescue
(Festuca violacea, Poaceae) to form mats
which stabilise the slope
Asexual reproduction, which is also called vegetative or clonal reproduction, generates exact copies
of the original individual called clones. Asexual reproduction is a more reliable form of reproduction
than sexual reproduction as it is independent of the season, of successful pollinisation and of seed
dispersal. However, this mode of reproduction does not increase genetic diversity, which limits the
evolution of species and their adaptation to changes in their environment. Alpine plants often utilize
both types of reproduction, increasing their chances of reproduction in difficult environments.
Numerous shrubs reproduce asexually by layering, in which buds located on branches lying on the
Diagram showing the production, starting
with a mother plant (left), of successive clones
from a horizontal stem (stolon or rhizome)
The foxtail grass (Alopecurus gerardi,
Poaceae) has rhizomes which produce
clones of the mother plant at their extremities
ground begin to develop their own roots (such as in Rhododendrons and the Green Alder). In other
species, plants can produce spreading aboveground stems called stolons (such as for Geums), or
underground stems called rhizomes, which do not have green leaves and whose buds can produce
clones (such as in numerous Poaceae, e.g. Alopecurus gerardi)
Some plants produce bulbs, which are fleshy buds which detach from the base of leaves and produce
clones of the mother plant (such as in the alpine bistort, and the orange lily).
It is estimated that for some plants such as Carex curvula, the dwarf willow and the alpenrose, the same
Sexual reproduction (flowers) in the alpenrose
(Rhododendron ferrugineum, Ericaceae)
which also uses clonal reproduction via
layering
clone can be aged numerous hundreds, or even thousands of years old.
Flowers (sexual reproduction) and bulbs
(clonal reproduction) in the orange lily (Lilium
bulbiferum var bulbiferum, Liliaceae)
53
Botanical Lessons
Systematics and classification (1/2)
A drawing of a peony from the book "Éléments
de botanique, ou méthode pour connaître les
plantes" published by Tournefort in 1694
Berardia subacaulis Vill., a species described
and named by the botanist from the
Dauphine region, Dominique Villars, in 1789
Systematics is that part of botany that aims to classify plants into group’s best reflecting their similarities
and differences. The criteria on which this classification is based are morphological characteristics
ANCESTRAL GROUPS
(structure of the flowers and vegetative parts), and more recently cytological characters (cell contents
MONOCOTYLEDONS
Commelinales
Poales
Asparagales
Liliales
Dioscorales
The Greek philosopher Theophrastus (370-285 BC) developed the first plant classification for 480 plants
Alismatales
Ranunculales
depending on their size (tree, shrub, or herb) and certain floral characteristics. The French botanist de
Buxales
Tournefort (1656-1708) established a classification of plants according to the structure of their flowers and
Fagales
Rosales
Fabales
Oxalidales
the first corresponds to the genus and the second to the species, followed by the name of the author who
first described it. The species are grouped into genera and then into families. For example, the belier peony
DICOTYLEDONS
things, called binomial, which is still used today. Each species is identified by two Latin (or Greek) names:
Malvales
Brassicales
Sapindales
Geraniales
Saxifragales
Caryophyllales
Ericales
illustrated opposite is the species arietina, within the genus Paeonia (peony), which belongs to the family
Gentianales
Lamiales
Salanales
Boraginaceae
Paeoniaceae.
Asterales
Dipsacales
AToday, the comparison of DNA sequences allows the further refinement of classifications based on
centuries of methodical observations, and the adoption of a phylogenetic approach providing
Plant labels from the garden using the
nomenclature created by Carl von Linnaeus
Magnoliales
Laurales
and structure) and genetics (DNA sequences).
fruits. It was the Swedish naturalist Carl von Linnaeus who developed a universal nomenclature of living
Carl von Linnaeus (1707-1778)
Amborellales
Nymphaeales
Piperales
information on the evolutionary history of different species and their evolutionary relationships.
Apiales
The phylogeny of flowering plants derived
from the comparison of DNA sequences. The
links represent evolutionary relationships. The
names shown on the right are the "orders"
which regroup several families. For example
the "Ranunculales" contain the families
Ranunculaceae and Papaveraceae
53
Botanical Lessons
Systematics and classification (2/2)
Alpine Columbine (Aquilegia alpina), a
nationally rare and protected species. Note
the hooked nectar spurs
Meadow-rue (Thalictrum aquilegifolium), with
its white flowers with numerous stamens. To
the right, the yellow globeflower (Trollius
europaeus)
Identification key of the principal genera of the Rannunculaceae family present in the Alps
For each plant in the rockery, choose between the two alternatives at level 1, and then continue similarly for each choice until arriving at one of the 12 genera
(Clematis, Delphinium, Aconitum, etc.). In the case of the genus Aconitum, identify the three alpine species. You can verify your identifications using the plant labels
Diagram of the structure of a flower: sepals
in green, petals in white, stamens in yellow,
fruits (achenes) in dark green
1. Leaves opposite, climbing plant
1. Leaves alternate, non-climbing plants
2. Flowers irregular, with only one plane of symmetry (zygomorphic)
2. Flowers regular, with multiple planes of symmetry (actinomorphic)
3. Flowers with a nectar spur
3. Flowers without nectar spurs
4. Flowers forming a yellow ball (the stamens and pistil are not visible
4. Flowers open (the stamens and pistil are visible)
5. Flowers with 5 hooked nectar spurs
5. Flowers without nectar spurs
6. Flowers with small green sepals and small hooked petals
6. Non matching characteristics
7. Flowers with petals and sepals both present and distinct
7. Flowers with only one type of sterile part (sepals), or completely without petals and sepals
8. Three sepals, flowers purple, blue or white
8. Five sepals, flowers yellow or white
9. Large sepals, resembling petals and very visible and strongly coloured
9. Four small sepals that fall very early, coloured stamens, highly dissected compound leaves
10. Five yellow-orange sepals, kidney shaped leaves
10. More than 5 white, purple or pale yellow sepals, very dissected leaves
11. Fruits (achenes) with a long feathery style ; Plants often covered with long hairs
11. Fruits (achenes) with deciduous style. Plants generally with few hairs
CLEMATIS
2
3
4
DELPHINIUM
ACONITUM see below
TROLLIUS
5
AQUILEGIA
6
HELLEBORUS
7
8
9
HEPATICA
RANUNCULUS
10
THALICTRUM
CALTHA
11
PULSATILLA
ANEMONE
Wolfsbane (Aconitum lycoctonum), an
extremely toxic species
A key to some alpine species of the genus Aconitum, all highly toxic species
Kupher’s ranunculus (Ranunculus kupferi), a
species from wet alpine grasslands
1. Flowers yellow
1. Flowers blue
2. Narrow helmet, much taller than wide. Leaves with large lobes
2. Helmet only just taller than wide. Leaves with filliform lobes
2
Aconitum napellus
Aconitum lycoctonum
Aconitum anthora
Alpine anemone (Pulsatilla alpina): the fruits
(achenes) have a long feather-like style
which grows after fertilisation