In this article we will discuss about:- 1. General Features of the Rosaceae 2. Divisions of the Rosaceae 3. Position and Affinity 4. Number and Distribution 5. Commonly Occurring Plants 6. Economic Aspects.
General Features of the Rosaceae:
Habit — Herbs, shrubs or trees.
Leaves — Alternate, simple or compound, stipulate (stipules adnate).
Flowers — Bisexual, regular, perigynous with a disc.
Calyx — Sepals 4 or 5, persistent.
Corolla — Petals 0 or many, imbricate, deciduous.
Androecium — Stamens many, in whorls, incurved.
Gynoecium — Carpels 1 or more, free; ovary superior; ovules 1 or more in each cell.
Fruit — Achene, berry or drupe.
Divisions of the Rosaceae:
On the basis of floral construction, the Rosaceae is divided into six subfamilies:
Subfamily I. Chrysobalanoideae:
Thalamus deeply cup shaped. Flowers irregular. Stamens sometimes monadelphous. Carpel 1. Examples: Acioa, Chrysobalanus, Hirtella, etc.
Subfamily II. Neuradoideae:
Thalamus cup shaped. Carpels 5-10, united. Examples: Grielum and Neurada.
Subfamily III. Pomoideae:
Thalamus deeply concave. Stamens many. Carpels 5, somewhat united and adnate to thalamus; ovules 2 in each carpel. Fruit a pseudocarp or pome. Examples: Cotoneaster, Pyrus, etc.
Subfamily IV. Prunoideae:
Thalamus cup shaped. Stamens 10,20 or more. Carpel 1, containing 2 ovules. Fruit a drupe. Example: Prunus.
Subfamily V. Rosoideae:
Thalamus concave. Carpels many and free; ovules 2 in each carpel. Examples: Fragaria, Potentilla, Rosa, Rubus, etc.
Subfamily VI. Spiraeoideae:
Thalamus somewhat flat, but never deep or convex. Stamens 10 to many. Carpels 5, free, located in centre. Examples: Spiraea and Quillaja.
Position and Affinity of the Rosaceae:
The Rosaceae comes under the Rosales, although many have included the Leguminosae under the same order and some have put them in separate orders.
The members of the Rosaceae are very much like those of the Ranunculaceae in some respects. The number of floral parts is similar in the two families, but in the Rosaceae the thalamus, instead of taking the form of a cone, is generally cup shaped with the carpels either standing up or embedded in the bottom of the cup.
The Rosaceae is allied to the Leguminosae as regards the perigynous flowers and monocarpellary pistil (in the Chrysobalanoideae and Prunoideae). A connection is also established with the Legume family by the genus Acioa where the flowers are zygomorphic with monadelphous stamens and a single carpel.
Number and Distribution of the Rosaceae:
The Rosaceae covers 115 genera and 3,200 species. The plants belonging to this family are widely distributed over most of the earth and are abundant in Europe, North America and eastern Asia.
Commonly Occurring Plants of the Rosaceae:
Indian Strawberry (Fragaria nilgerrensis Schlecht. ex J. Gay) is a trailing herb with globose and pale pink fruits.
Potentilla supina L. is an annual herb of Darjeeling, Shillong and other hill stations.
Primus cerasoides D. Don is found in the hills.
Pygeum acuminatum Colebr. is a tree with two seeded fruits.
Roses (Rosa alba L.. R. centifolia L.. R. damascena Mill., R. indica L.. R. involucrata Roxb.) are armed shrubs.
Bramble (Rubus hexagynus Roxb.) is a shrubby plant.
Economic Aspects of the Rosaceae:
The Rosaceae is economically important for edible seeds, such as Almond (Prunus amygdalus var. dulcis) and edible fruits, such as Coco plum (Chrysobalanus icaco), Quince (Cydonia vulgaris), Loquat (Eriobotrya japonica), Strawberry (Fragaria chiloensis, F. vesca. F. virginiana), Apple (Malus pumila), Medlar (Mespilus germanica), Apricot (Prunus armeniaca), Cherry (P. cerasus), Plum (P. domestica), Peach (P. persica), Pear (Pyrus communis), Blackberry (Rubus fruticosus).
Raspberry (R. idaeus), etc. Licania rigida (Brazil) yields ‘oiticica oil’ of commerce. The bark of Moquila utilis (Brazil) is used in making heat resistant pots. The dried inner bark of Quillaja saponaria (Andes) forms the commercial ‘soapbark’. Sorbus aucuparia yields timber. There are also a number of ornamentals, e.g., Cotoneaster, Crataegus, Geum, Kerria. Potentilla, Rosa and Spiraea.
No comments yet.