Fig. 547.—Diagram of Primula.
Family 28. Primulinæ.
The flowers are regular, ☿, hypogynous, and gamopetalous. The stamens are equal in number to the petals (Fig. [547]) and are placed opposite to them. The ovary is unilocular, with a free, central placenta with 1–many ovules.—The flower is a further development of the Diospyrinæ; the suppression of the calyx-stamens, which commenced in this family, is carried further in the Primulinæ, so that in the majority of cases no trace of them is present, but in certain species and genera (Samolus, Lysimachia thyrsiflora, Soldanella, certain Myrsineæ) some small bodies (scales, teeth, etc.) are found in the position of the suppressed stamens. Again, the lateral portions of the carpels are suppressed, so that the ventral placentæ with the ovules are separated from the dorsal portions, and are united into a free central placenta; this theory is supported by the branching of the vascular bundles, the development, and various comparative considerations.—Sn, Pn, A0 + n, Gn; where n = 4–8, generally 5. The carpels are placed opposite the sepals (Fig. [547]).
Order 1. Primulaceæ (Primroses). This order has many ovules attached to a thick, free, central placenta (Fig. [547]); style undivided with a capitate stigma; ovules semi-anatropous; fruit a capsule with many seeds.
All the plants belonging to this order are herbs; stipules wanting; the flower is most frequently 5-merous (S5, P5, A0 + 5, G5; except Centunculus and Trientalis). The corolla and capsule have various forms, but the capsule generally opens by teeth at the apex. The ovules are semi-anatropous (in Hottonia they are anatropous), and the seeds are therefore peltate, with the hilum situated in the centre of one side. The endosperm is fleshy or horny. The flowers are borne either in racemes or in umbels; as bracteoles are typically absent (Fig. [547]), cymose branching does not occur.
Fig. 548.—Primula: dimorphic flowers. A short-styled; B long-styled.
Fig. 549.—Cyclamen persicum.