A raceme () or racemoid is an unbranched, indeterminate type of inflorescence bearing flowers having short floral stalks along the shoots that bear the flowers. The oldest flowers grow close to the base and new flowers are produced as the shoot grows in height, with no predetermined growth limit. Examples of racemes occur on mustard (genus Brassica), radish (genus Raphanus), and orchid (genus Phalaenopsis) plants.
Definition
A
raceme or
racemoid is an unbranched, indeterminate type of
inflorescence bearing pedicellate
(flowers having short floral stalks called
pedicels) along its axis.
In
botany, an
axis means a shoot, in this case one bearing the flowers. In indeterminate inflorescence-like racemes, the oldest flowers grow close to the base and new flowers are produced as the shoot grows in height, with no predetermined growth limit.
A plant that flowers on a showy raceme may have this reflected in its scientific name, e.g. the
species Actaea racemosa. A compound raceme, also called a
panicle, has a branching main axis. Examples of racemes occur on mustard (
genus Brassica) and radish (genus
Raphanus) plants.
Spike
A
spike is an unbranched, indeterminate inflorescence, similar to a raceme, but bearing sessile flowers (sessile flowers are attached directly, without stalks).
Examples occur on Malabar nut (
Justicia adhatoda) and chaff flowers (genus
Achyranthes).
A
spikelet can refer to a small spike, although it primarily refers to the ultimate flower cluster unit in grasses (
Poaceae) and sedges (family
Cyperaceae),
in which case the stalk supporting the cluster becomes the pedicel. A true spikelet comprises one or more florets enclosed by two
(sterile
), with flowers and glumes arranged in two opposite rows along the spikelet. Examples occur on rice (species
Oryza sativa) and wheat (genus
wheat), both grasses.
Catkin
An
catkin is very similar to a spike or raceme "but with subtending bracts so conspicuous as to conceal the flowers until pollination, as in the
Pussy willow,
alder, and
birch...". These are sometimes called
amentaceous plants.
Spadix
A
spadix is a form of spike in which the florets are densely crowded along a fleshy axis and enclosed by one or more large, brightly–colored
called
. Usually the female flowers grow at the base, and male flowers grow above.
They are a characteristic of the family
Araceae, for example jack–in–the–pulpit (species
Arisaema triphyllum) and wild calla (genus
Calla).
Examples
File:Traube (inflorescence).svg|
File:Inflorescences Spike Kwiatostan Kłos.svg|
File:Kätzchen (inflorescence).svg|
File:Kolben (inflorescence).svg|
File:Spathoglottis flwrs reduced.jpg|The inflorescence of Spathoglottis plicata, a terrestrial orchid, is a typical raceme
File:Backlit xeronema flower raceme.jpg|Tightly packed raceme of Xeronema callistemon, with prominent red
File:Pycreus.jpg|Every radiating unit in this inflorescence of a Cyperus sedge is a spikelet composed of small flowers (florets) arranged in two ranks
Etymology
From classical Latin, a
racemus is a cluster of grapes.
[Oxford English Dictionary. Raceme 2. Bot. A type of inflorescence in which the flowers are arranged on short, nearly equal, lateral pedicels, at equal distances along a single elongated axis]
See also
