Part 115. The Linden Family - Various Plant Groups

Part 115. The linden family (Tiliaceae.) Examples: jute (Figs. 218 I, II), and linden (Figs. 251, 252).

See the formulas of Corchorus, Tilia, and Tiliaceae on pages 410, 411.

The bracts of lindens (Tilia) and the androecium and fruit of the family present the chief peculiarities which call for present notice. The bracts of jute (Corchorus) present no special peculiarities. In lindens, however, the lowermost bract of the flower-cluster is large, forming a sort of involucre, and adheres for a considerable distance to the peduncle. Jute flowers, which have the stamens in two whorls of five each, thus conforming to the numerical plan of the other floral organs, afford the simplest condition. In other species the stamens appear to be indefinite in number, but close examination would show them to be grouped into five clusters opposite the five petals. Each cluster is taken to represent the branches of a single one of the inner whorl of stamens, in much the same way that a pair of long stamens in the mustard family represent, as we have seen (section 110), a single branched stamen.

The fact that the stamen-groups are opposite the petals (hence regarded as being of the inner stamen whorl) is expressed by placing the sign || between P and FA.

Stamens in five clusters are said to be pentadelphous.¹ The stamens of the linden are always pentadelphous, and sometimes each cluster includes a staminode to which the anther-bearing filaments are coalescent. Throughout the family two pollen-sacs are borne by each filament which, however, divides more or less at the tip into a short stalk for each sac.

¹ Pen"-ta-derphous - Gr. pente, five. FA ∞ ÷ 5.

The fruit of jute is a capsule dehiscing by dorsal sutures into valves attached to the radial partitions. Such dehiscence is called loculicidal.² In lindens only one of the five carpels ripens, and commonly only one of the seeds which it contains. The pericarp becomes somewhat drupaceous so that the product of each flower resembles a small round almond. But a cluster of these nut-like fruitlets is formed by each inflorescence, and this cluster, borne on a common peduncle to which the bract still adheres, separates at maturity as a whole from the tree. The dry bract serves excellently as a sail to carry the fruit-cluster before the wind over smooth ground or a crust of snow.

² Loc'u-li-ci"dal - L. loculus, a compartment; coedere, cut, because it is as if each compartment were cut into, so that in cross-section each division has a form something like the sign J_ which is used to distinguish this type of capsule in the formula of Corchorus.

The family comprises mostly woody plants having mucilaginous juices; and often fragrant flowers with petals imbricate and distinct; stamens numerous, pentadelphous, and free; anthers with two pollen-sacs; and styles coalesced throughout.