FOLIAGE AND THEIR FUNCTIONS TWO

In the last article on foliage and their functions I looked at the function of foliage of the trees and plants that they adorn. In this article we shall observe the shape of the foliage including the terms that botanists attribute to these shapes.  The term for studying these shapes is leaf Morphology.

I will once again endeavour to keep the text as simple as possible so that interest is not lost or bogged down in botanical jargon. Even the tips of the leaves have their own botanical terms and it helps in identifying foliage when one has the basic awareness of these terms. Most wild flower books and indeed many books identifying cultivated flowers will use these words when describing the foliage of plants.

Many different words describe the many different shapes of a leaf tip, below is a cross section of these terms. 

Accuminate from Latin accuminare -to sharpen. The tips of this type of leaf are long pointed, tapering into a prolonged narrow tip in a concave amnner.

Acute from Latin acvere -to sharpen  from acus-needle, this type of leaf end in a sharp, but not prolonged tip.

Cupsidate--from Latin cupsidare -to make pointed from cupus a point. These leaves narrow to a point.

Obtuse from Latin obtusus meaning dulled this type are rounded or blunt.

Truncate from latin truncare meaning to lop, ending abruptly with a flat end, that looks cut off.

Apex toothed.- teeth at the tip. 

Next we consider the botanical terms when describing the base of the leaf. Acumiate and acute see above.

Auriculate from Latin auris an ear the base of these leaves ends with an ear shaped lobed.

Cordate-heart shaped with a notch towards the stalk.

Cuneate- wedge shaped.

hastate from Latin hasta- a spear, shaped like a halbard basal lobes pointing outwards.

renifirm from Latin renis, meaning a kidney. Kidney shaped but rounder and broader than long.

rotund, rounded leaves.

saggitate--from Latin sagitta an arrow, arrow shaped foliage with acute basal lobes pointing down wards.

truncate-ending abruptly  as though cut off.

Let us now review the surface of the leaf. The botanical names to describe the leaf surface include Farinose-bearing very short waxy, whitish powder.

glabrous- from Latin glabra, meaning bald or smooth.

glaucos- from Latin glaucus meaning silvery bluish-green with a whitish bloom,

glutinos-viscid and sticky.

pubescent-covered with erect hairs Especially soft and short ones.

rugose from Latin ruga a wrinkle. leaves are deeply wrinkled.

verrucose-from Latin verruca-a  wart leaves covered with a warty prominence.

viscid from latin viscum -mistletoe {or bird lime]-- covered with sticky secretions.

Many species of plants and trees have evolved to have their surfaces covered with hairs which vary greatly in thickness and shape.This covering of hairs on differing species have various functions. Some types hold moisture in to prevent water loss. Others reflect the rays of the sun so as to protect the surface from getting to hot . hairs on many perennials are to protect the surface from frost and ice.

The hairs { Botanist refer to them as trichomes} have many botanical terms alluding to the type of hairs, their texture or appearance. For instance arichnose hairs are very fine, entangled so has to give a cobwebby appearance.

glandular-- with a gland at the tip of the hair.

lanate--with woolly hairs.

Stellate--with star-shaped hairs.

Tomentose ---densely matted with soft white woolly hairs.

The surface of the leaves may be waxy which reduce water loss. Succulent leaves store water and other nutrients. Some have aromatic or toxic qualities to prevent grazing. Some plants have leaves that are adapted-a transformation into tendrils to help them climb. Many members of the Fabiaceae bean family, adopt this strategy. Others adapt a transformation into bracts.

Bracts are modified leaves, especially when associated with a reproductive structure such as a flower. Bracts are often different from the form of true leaves[But not always so} being larger or smaller, or differing in colour or texture to the unmodified leaves of the plant. Some are brightly coloured and thus are there to attract pollinators. 

Bracts that appear in whorls surrounding the stem beneath the flower are collectively known as the involucre.  The daisy family in particular have many species with such bracts are present.

Leaves that grow in shade tend to be thinner and adorned with less hairs and of a larger size than those on the same plant/tree that are exposed to direct sunlight. The foliage of plants that that tenant dry, hot regions, generally have thicker leaves and of a more leathery texture. many will be adorned with succulent leaves, and, in some cases lack foliage altogether, in this case the stems tend to be densely covered by hairs. Many desert plants have modified leaves in the form of spines.

Plants of the Fabiaceae {pea and bean family ] have modified leaves that turn into tendrils to help them climb and for support.

LINEAR--greater stitchwort--Stellaria holostea.

Lance shaped--ribwort plantain-Plantago lanceolata.

Elliptical--Bog bean Menyanthes trifoliata. 

Oblong--primrose Primula veris.

Spoon shaped--common daisy Bellis perennis.

Kidney shaped, butterbur, Petasites hybridus.

heart shaped-lesser celandine. {see photograph above.}

Arrow shaped--sheep's sorrel, Rumex acetosella.

Trifoliate---Clover, Trifolium species.

Digitate---Crane's-bill species

Palmate lobed, Lady's mantle Alchemilla species.

Pinnate---Meadow sweet, Filipendula ulmaria

PINNATE WITH TENDRIL---Bush vetch , Vicia sepium,

Bi pinnate--Fens such as the male fern.

3-4 times pinnate -Bracken Pteridium aquilinum

finely toothed-sawwort, Serratula tintoria.

Coarsely toothed,--dog rose Rosa regusa

Alternate, creeping buttercup.Ranunculus repens.

Sheathed. Angelica sylvestris.

The leaves of ferns are called fronds.

As we have seen leaves are important to plants and trees they are also vital to humans for food such as leaf vegetables and leaf salads, and of course for medicinal purposes. They also have an importance in aesthetic values such as flower arrangements. 

In the next article which will be the fourth in this series of how plants live and thrive we move on to the flower and its components.

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