Classification of Primulales: 2 Families | Dicotyledonae

In this article we will discuss about the classification of Primulales. According to Hutchinson, Primulales consists of two families:- 1. Mysinaceae 2. Primulaceae.

Family # 1. Myrsinaceae:

Myrsinaceae are evergreen trees or shrubs. Leaves are simple, alternate, entire, exstipulate; usually leathery. Inflorescence usually axillary, racemose or cymose or corymbose, rarely paniculate. Flowers are regular, bisexual, rarely unisexual hypogynous, bracteate.

Sepals usually 5, free or connate at base, imbricate, persistent. Petals as many as sepals, mostly united to form a rotate or salver-shaped corolla, rarely free, contorted, imbri­cate or valvate. Stamens as many as and inserted on the petals; filaments very short; anthers bilocular, introrse; connective slightly prolonged.

Carpels 3-6; ovary syncarpous, unilocular, superior, rarely semi-inferior; ovules 1 or few, sunk in the tissue of the free central placenta; style with a slightly lobed stigma. Fruit a berry or drupe. Seeds with copious fleshy endosperm and straight embryo, eodosperm often semi- ruminate.

The ordinary floral formula would be:

Corolla is gamopetalous in most cases but free petals are found in Embelia. Stamens are usually free but monadelphous androecium occurs in Ardisia and in this genus stamens develop before the corolla as in the family Primulaceae. Stamens are syngenesious in Amblyanthus. In Aegiceras the anther lobes are transversely septate.

The family consists of about 800 species under 32 genera occurring in the tropical and subtropical parts of the old world and also found in Mexico. In India a few species of Maesa are found in the lower elevations of the Himalayas, several species of Ardisia in the plains and Aegiceras corniculatum (L.) Blanco occurring in the tidal forests of Sunder bans.

Myrsinaceae is closely allied to Primulaceae and Theophrastaceae, the three families being included in one order by most workers. The family is practically of ho economic importance except that a few are culti­vated as ornamental trees or shrubs, e.g. Jacquinia ruscifolia Linn., Ardisia solanacea Roxb. etc. Embelia ribes Burm. f. is considered to have medicinal properties.

Family # 2. Primulaceae:

Primulaceae are perennial or annual herbs, rarely suffruticose, often with corms, tubers or rhizomes. Leaves are simple, alternate, opposite or whorled, exstipulate, sometimes radical, fari­nose or gland-dotted. Inflorescence umbellate, racemose or spicate, or flowers solitary.

Flowers are pentamerous, actinomorphic, very rarely zygomorphic, hermaphrodite, usually hypogynous. Calyx 5-partite, imbricate, persistent. Corolla rotate, funnel- shaped or campanulate, lobes usually 5, imbricate or contorted.

Stamens as many as corolla-lobes, inserted on the corolla-tube opposite the corolla-lobes; filaments short, free; anthers introrse, dehiscing longitudinally; an outer whorl of staminodes is rarely present.

Carpels usually 5, syncarpous; ovary 1-chambered, superior or rarely half-inferior; ovules many on free central placentas, amphitropous or semi-anatropous, with 2 integuments; style long or short with capitate stigma. Capsule dehiscing by valves or transversely; seed with a small embryo and fleshy or horny endosperm.

Corm is found in species of Cyclamen. Some species of Lysimachia are undershrub’s. In the floating aquatic genus Hottania the leaves are heterophyllous, the submerged ones are pinnate. Coris has zygomorphic flowers.

Flowers in Primula are dimorphic, having stamens and styles of different length in flowers of same plant. In Centunculus flowers are 4-merous, in Lysimachia 6-merous and in Trientalis they are 9-merous. The flowers of Glaux are ape talons.

In Pelletiera corolla is polypetalous. An outer whorl of staminodes is present in Soldanella and Samolus. Corolla is reflexed in Cyclamen and Dodecatheon. The overy is semi-inferior in Samolus. Fruits of Anagallis, Centunculus and Soldanella are pyxis where the top falls off as a lid.

Floral formula:

The family comprises 28 genera with about 1000 species occurring mostly in temperate countries of the northern hemisphere, having many artic and alpine species. In India several species of Primula, Lysimachia and Androsace are found in the Himalayas and the hills of Assam while Anagallis arvensis Linn., Centunculus tenellus Duby and Androsace saxifragaefolia Bunge occur in the plains.

The family is divided into 5 tribes:

I. Primuleae (Androsaceae):

Ovary superior; corolla imbricate; capsule usually valvular.

II. Cyclamineae:

Ovary superior, corolla convolute, petals reflexed; capsule valvular; plants with corm.

III. Lysimachieae:

Ovary superior; corolla convolute; capsule, valvular or with circumcissile dehiscence; corms absent; petals not reflexed.

IV. Samoleae:

Ovary semi-inferior; corolla imbricate.

V. Corideae:

Flower zygomorphic; calyx spiny.

The tribe Corideae with a single genus Coris is placed by some in a monotypic family Coridaceae.

The family is allied to Myrsinanaceae and Theophrastaceae and the three families are included in one order Primulales by most authors. It is also allied to Plumbaginaeeae which family is placed in Primulales by Hutchinson who removes Myrsinaceae and Theophrastaceae to a distinct order Myrsinales.

Primulaceae is related to Caryophyllaceae and also to Theaceae to some extent. Bessey, Wettstein, Hallier and Hutchinson are of the opinion that Primulaceae and the order Primulales originated from Caryo­phyllales. Cronquist considers that Primulaceae and the order Primulales originated from Theales while he does not rule out the possibility of Caryophyllous origin of the group.

The family is not of much economic importance. Species of Primula are the Prim­roses of our garden, the most popular of which are P. vulgaris Huds. and P. sinensis Sabine Species of Cyclamen are also cultivated for the beautiful flowers.

Lysimachia vulgaris yields a yellow die and is also a febrifuge. Cyclamen purpurascence and Anagallis arvensis Linn, are poisonous; the former contains the glucoside cyclamin and the latter a glucoside similar to saponin.