Vernation
Vernation is the formation of new
leaves or
fronds. In plant anatomy, it is the arrangement of leaves in a bud.
In
pine trees, new leaves are short and encased in sheaths. Each leaf bundle consists of 2 to 5 needles. All the leaves on one section of branch grow in length together. In the
cabbage, new leaves are folded over, each covered by the previous leaf.
Encyclopedia
Vernation is the formation of new
leaves or
fronds. In plant anatomy, it is the arrangement of leaves in a bud.
In
pine trees, new leaves are short and encased in sheaths. Each leaf bundle consists of 2 to 5 needles. All the leaves on one section of branch grow in length together. In the
cabbage, new leaves are folded over, each covered by the previous leaf.
Circinate vernation
Circinate vernation is the name given to the manner in which new
fern fronds emerge. As a new fern frond is formed, it is tightly curled so that the tender growing tip of the frond is protected within a coil. At this stage it is called a
crozier or
fiddlehead . As the lower parts of the frond expand and toughen up, they begin to
photosynthesize, supporting the further growth and expansion of the frond. In the case of many fronds, such as that of the Australian tree fern in the picture at right, long hairs or scales provide additional protection to the growing tips before they are fully uncoiled.
Circinate vernation may also be observed in the extension of pinnae, or leaflets, in the compound leaves of the
Cycads .
