A most remarkable form of vegetation in the north-west is the gouty-stemmed tree (Adansonia Gregorii), one of the Malvaceae.
The chief of these silk cottons is kapok, consisting of the hairs borne on the interior of the pods (but not attached to the seeds) of Eriodendron anfractuosum, the silk cotton tree, a member of the Bombacaceae, an order very closely allied to the Malvaceae.
When the flower is sessile the bracts are often applied closely to the calyx, and may thus be confounded with it, as in the order Malvaceae and species of Dianthus and winter aconite (Eranthis), where they have received the name of epicalyx or calyculus.
This arrangement is characteristic of the flower-buds of Malvaceae and Apocynaceae, and it is also seen in Convolvulaceae and Caryophyllaceae.
Thus, in Malvaceae the corolla is contorted and the calyx valuate, or reduplicate; in St John's-wort the calyx is imbricate, and the corolla contorted.