Classification of Fagales: 2 Families | Dicotyledonae

In this article we will discuss about the classification of Fagales. According to Engler, Fagales consists of two families:- 1. Fagaceae 2. Betulaceae.

Family # 1. Fagaceae:

Fagaceae are trees or rarely shrubs, deciduous or evergreen; sub-epidermal cork usually deve­lops; tanin is often contained in the cells. Leaves are simple, alternate, stipulate; stipules scaly, deciduous, protecting the vegetative bud.

Flowers are unisexual, solitaryey disposed or in clusters along the catkins or in small spikate heads, rarely solitary; the flower culsters on the catkins are usually in cymes forming often a dischasium.

Each flower of Fagaceae or a flower cluster is in the axil of a bract and surrounded by an involucre of bracteoles which in female flowers enlarge and form the so called cupule of the fruit. Perianth in one whorl, segments scale-like 4-7 in males and 6 or rarely 4 in females.

Stamens 4—many, free; filaments filiform, anthers bilobed, dehiscing by vertical slits. Ovary inferior, tricarpellary syncarpous, 3-celled with 2 pendulous ovules in each cell; styles 3, free to the base; ovules anatropous, with 2 integuments. Nuts 1-3 enclosed at base by the cupule. Seed with a large embryo and no endosperm.

Plants of Fagaceae are monoecious except in Nothofagus which has dioecious plants. Bisexual flowers are rarely found. Usually male flowers occur at the upper part of the caktin while the females occupy the lower portion. In some species of Castanea male and female flowers occur in separate catkins in the same plant.

The cupule varies in structure in different genera; in Castanea it is spinous, in Fagus four bristly segments represent the cupule, in others it is cup-shaped enclosing the basal portion of the nut.

A cupule may have only one nut or 2 or 3. According to Prantle the cupule is an outgrowth of the axis of the flower and Celakovsky considers it to be an outgrowth of the thalamus; most others think it to be an involucre of bracteoles.

Cork is found in all species developed sub-epidermally but is more deep seated in Nothofagus. The vessels have simple and scalariform pits and are arranged singly. The flowers are wind pollinated but in Castanea they are entomophillous.

The family of Fagaceae consists of about 900 species in 8 genera and occurs in the N. Tem­perate zone, in the hills of the Mediterranean region and of the Asiatic countries. It is found in the Himalayas and in the Khasi hills where several species of Quercus, Pasania and Castanea are found.

Many species of Quercus are the oaks yielding very good quality of timber suitable for ship-building. Species of other genera also yield good timber. Quercus suberLinn of the Mediterranean region yields bottle-cork.

Fagaceae is closely related to Betulaceae and both are placed under one order by most workers. Hutchinson and most others consider that the family has been derived from Hamamelidaceae. This is supported from anatomical evidence also.

Family # 2. Betulaceae:

Betulaceae are trees and shrubs, usually deciduous, resin secreting glands present in young branches. Leaves of Betulaceae are simple, alternate, stipulate; stipules deciduous.

Flowers of Betulaceae are small, uni­sexual, in distinct male and female catkins on the same plant; bracts and bracteoles present; the catkins bear dense clusters of 3 or 2-floweres in cymes each Subtended by a bract; the lateral flowers are provided with bracteoles, in the central flower usually the bracteoles are lacking; the bracts and bracteoles often- unite to form a protec­tive covering of the fruit.

Perianth present or absent, often scale-like, 2 or 4 or more, persistent. Stamens 4, opposite to perianth-lobes, often stamens only 2, or more than 4, splitted from above with one anther lobe on each splitted filament; anthers extrorse dehiscing longitudinally.

The ovary inferior, bilocular, with one pendulous ovule in each cell; styles 2 persistent; stigma clavate; ovule anatropous, with one integument; only one ovule in an ovary matures to a seed, the other becomes abortive.

Fruit a small nut, shortly winged or not, subtended or enclosed by the united bract and bracteoles forming a cover-scale or a cupule, the cover-scales detach from the axis or are woody and remain attached to the axis so the entire fruiting catkin resembles a small cone. Seed with a straight embryo and no endosperm; cotyledons large, con­taining oily substance.

The family of Betulaceae comprises a little over 100 species in 6 genera, distributed in the N. Temperate region and in hills of tropical countries. Several species of Betula and Alnus occur in the Himalayas and Khasi and Naga Hills. Some species yield valuable tim­ber; the wood is good for charcoal. Corylus avellana Linn, produces the Hazel-nut and C. tabulosa Linn, and C. colurna Linn, also yield edible nuts.

The bark of Betula contains tanin and is used to tan leather; the spring sap of some species of this genus is sweet and is often used for manufacturing liquor. The bark of Betula utilis D. Don comes off in very thin paper like strips and at one time used as paper in India, particularly in Nepal where it is known as “Bhurjapatra”.

Betulaceae is closely allied to Fagaceae and both the families are supposed to have originated from Hamamelidaceae or from a stock allied to Hamamelidaceae. The family is subdivided into 2 tribes, viz., Betuleae and Coryleae which are treated as- 2 distinct families by Hutchnison as Betulaceae and Corylaceae.