Part 60

α. Only lateral nectaries. Generally a silicula or indehiscent fruit.--Cochleariinæ.

β. Generally a siliqua, more rarely a silicula or transversely-divided or indehiscent fruit. Nectaries generally lateral and median.--Alliariinæ; Sisymbriinæ; Vellinæ; Brassicinæ; Cardamininæ.

B. Hairs collectively or partially branched, very rarely entirely absent; glandular hairs are sometimes also present.

1. SCHIZOPETALEÆ.

2. HESPERIDEÆ. Stigma strongly developed above the placenta; style undivided or prolonged above the placentæ into shorter or longer lobes.

a. Surface cells of the replum, not divided diagonally.--Capsellinæ; Turritinæ; Erysiminæ; Alyssinæ.

b. Surface cells of the replum divided diagonally.--Malcolmiinæ; Hesperidinæ; Moricandiinæ.]

POLLINATION. Honey is secreted by the nectaries mentioned above; but the position of the stamens is not always the most favourable for pollination by insects (in these flowers the honey-seeking insect must touch the anthers with one of its sides and the stigma with the other), and self-fertilisation is common. In some species (Cardamine pratensis) the long stamens turn their anthers outwards towards the small stamens, so that 3 anthers surround each of the two large entrances to the nectaries.

1200 species (180 genera), especially in the cold and temperate parts of the Old World (Europe, W. Asia). Many are weeds in this country, e.g. Wild Cabbage (Brassica campestris), Charlock (Sinapis arvensis), Wild Radish (Raphanus raphanistrum) and others.--The order is acrid and oleaginous. Oil is obtained from many of the oil-containing seeds, especially of the Rape (Brassica napus), Summer-Rape (the oil-yielding cultivated form of the Field-Cabbage) and Camelina. Several are pot-herbs or fodder plants, e.g. Cabbage

(Brassica oleracea) with its numerous varieties: Cauliflower (var. botrytis; the entire inflorescence is abnormally branched and fleshy), Kohlrabi (var. gongylodes, with swollen, tuberous stem), Kale, Red-Cabbage, White-Cabbage, etc.; B. campestris, var. rapifera (Turnip); B. napus, var. rapifera (Swede); Raphanus sativus (Radish from W. Asia), R. caudatus (long Radish); Nasturtium officinale (Water Cress), Lepidium sativum (Garden Cress), and Barbarea præcox (Early Cress); Crambe maritima (Sea-Kkale). The seeds of the following are especially used as spices: (the flour of) Melanosinapis (Black-mustard), and Sinapis alba (White-mustard), which are officinal like the root of Cochlearia armoracia (Horse-radish, E. Eur.). The herbaceous parts of Cochlearia officinalis and danica are medicinal.--A blue dye (woad) is extracted from Isatis.--Ornamental plants: Cheiranthus cheiri (Wallflower), Matthiola (Stock), Iberis, Hesperis, Lunaria, and others (especially from S. Eur.). Sweet-scented flowers are rare.

Order 4. =Capparidaceæ= (=Capers=). The relationship with the Cruciferæ is so close that certain forms are with difficulty distinguished from them. The diagram of the flower is the same in the number and position of its parts, but it differs in the modifications which occur in the development of the stamens. In some genera all 4 stamens are undivided; in others both the 2 median ones are divided as in the Cruciferæ (6 stamens, but not tetradynamous) (Fig. 414); in other genera only 1 of these; in other instances again they are divided into more than 2; and finally the 2 lateral ones also may be found divided, so that indefinite stamens occur (Fig. 415). The bicarpellate gynœceum is unilocular (without replum), but more than 2 carpels may occur. The ovary is elevated on a stalk (sometimes as much as 1 foot in length); also between the stamens and corolla a similar stalk may be found (Fig. 414). The fruit is long and siliquose (Cleome, Polanisia, Gynandropsis), or a berry (Capparis). Endosperm absent. Some have zygomorphic flowers. Gamosepalous calyx and perigynous flowers also occur.--350 species; especially in the Tropics. The majority are trees and shrubs, and they differ also from the Cruciferæ in having distinct stipules present in some species.

“Capers” are the flower buds of the climbing, thorny shrub, Capparis spinosa (Fig. 415), which grows in the Mediterranean.

Family 11. =Cistifloræ.=

The flowers in this family are perfect, regular (except Resedaceæ, Violaceæ), hypogynous, the perianth-leaves free (a few have them slightly united), æstivation most frequently imbricate; they are eucyclic in the andrœcium, and most frequently in the other parts, and generally 5-merous with S5, P5, A5 + 5, G3, but other numbers also occur; several have indefinite stamens, but the stamens arise (where the development is known) in centrifugal order and are arranged, often very distinctly, in bundles; in other words, the large number of stamens is formed by the splitting of a small number (most frequently 5); a true spiral arrangement is never found. Gynœceum syncarpous, multicarpellary (Dilleniaceæ and a few Resedaceæ are apocarpous), most frequently the number of carpels is 3, forming a unilocular ovary with parietal placentæ, but parallel with this, multilocular ovaries, with the ovules placed in the inner angle of the loculi, are also found, and a few genera have a free, centrally-placed placenta. The fruit is most frequently a capsule. The dehiscence is never with a “replum,” i.e. the persistent frame of the placenta, as in the family Rhœadinæ. One half of the orders has endosperm (Violaceæ, Cistaceæ, Droseraceæ, Bixaceæ, Ternstrœmiaceæ, etc.), the other has no endosperm (Resedaceæ, Hypericaceæ, Elatinaceæ, Tamaricaceæ, etc.); some have a curved, the majority a straight embryo. ~The family is scarcely quite natural; in the future the orders will probably be arranged differently.~

Order 1. =Resedaceæ (Mignonettes).=--Herbs or small shrubs with spirally-placed leaves and very small, gland-like stipules (as in Cruciferæ); the ☿, hypogynous flowers are zygomorphic, and arranged in racemes or spikes typically without bracteoles. The zygomorphic structure is produced by the greater development of the posterior side of the flower, especially the petals and the nectary (“disc,” in Fig. 416 d) which is situated between the petals and stamens; in general there are 5–8 free sepals and petals, the latter consisting of a large scale-like sheath with a fimbriated blade (see Fig. 416); stamens numerous; carpels 6–2 united together; ovary unilocular with parietal placentæ, but the cavity of the ovary is not closed at the top. In Astrocarpus the gynœceum is apocarpous. The fruit is most frequently a capsule; the seeds are reniform, without endosperm, and the embryo is curved.

This order connects the Rhœadinæ with the Cistifloræ. It is closely allied to the Rhœadinæ by its external appearance, even by the smell and taste, the parietal placentation, structure of the seeds, the inflorescences, etc., whilst by the irregular flowers and the disc placed at the posterior side of the flower, it is allied to Capparidaceæ, but differs from this order in not having its characteristic number (2–4) and by the very different mode of dehiscence of the fruit, etc. It differs from the other orders of this family chiefly in the fact that the number of the perianth-leaves is not constantly 5. In Reseda luteola both the calyx and corolla appear to be 4-leaved, because the posterior sepal is suppressed, and the 2 posterior petals are united. Where there are 10 stamens, they stand in 2 whorls, i.e. in front of the sepals and petals; if there are several, their position depends upon the splitting.--Astrocarpus is remarkable for its apocarpous fruit and the position of the ovules on the dorsal suture of the carpel.

The yellow, flat disc at the back of the flower serves as a nectary, the honey being protected by the lobes of the petals. If pollination by insects is not effected, then self-pollination may take place, at all events in R. odorata.

45 species; the majority in the Mediterranean and in Persia. Reseda odorata (from Egypt) is cultivated on account of its sweet scent; R. luteola (“Dyer’s Weed”) yields a yellow dye.

Order 2. =Droseraceæ (Sundews).= Herbs, chiefly living on moors or in water, and whose leaves are adapted to catch and digest small animals. With regard to the flower, they are closely allied to the Violaceæ, especially to those with regular flowers. Drosera (Sundew) has a long-stalked scorpioid cyme with regular, ☿, hypogynous flowers, 5-merous as in Viola. S5, P5, A5, G3 (in a syncarpous gynœceum, with free, bifid styles and basal or parietally-placed ovules in the unilocular ovaries). The capsule opens also as in Viola, but, among other differences, the styles are free, the seeds very small, and surrounded by a loosely lying, thin shell. ~Drosera has radical, long-stalked leaves with the blade (Fig. 417) covered by numerous strong glandular hairs, placed on the edge and in the middle; when small animals are caught by these hairs, the latter and the entire blade close slowly over them dissolving and absorbing all the digestible matter as nourishment.~

Dionæa muscipula (Fly-trap; N. Am.) has the same appearance as Drosera, but the leaves are constructed as in Fig. 418. The stalk is flat and winged, the blade small, circular, with powerful, pointed teeth along the edge, and on its surface are 6 small bristles (A), which are very sensitive. When these are touched the blade quickly closes, folding along the midrib (B, C) and imprisoning the irritating object, the teeth round the edges fitting like the teeth of a trap. If it happens to be an insect or similar body, a digestive fluid is secreted which, like the gastric juice, dissolves the digestible portions. Aldrovandia vesiculosa (Central and S. Europe) captures small aquatic animals in a similar manner; it is a floating, aquatic plant, the two halves of its leaves also close together when irritated (Fig. 419).--Drosophyllum.

About 110 species; most of them in the temperate regions.

Orders 3 and 4. =Sarraceniaceæ and Nepenthaceæ.= These two orders are perhaps most closely allied to the Droseraceæ and agree with these, among other things, in the manner of taking nourishment. Like the Droseraceæ they absorb nitrogenous food from dissolved animal matter by means of their leaves, which are specially constructed both to catch, to retain, and to digest any small animals which may be caught. The SARRACENIACEÆ are North American marsh-plants (10 species) which have pitcher-like leaf-stalks, in the cavity of which a fluid (with properties approaching those of gastric juice) is secreted, and which bear at the apex a small, lid-like blade; these leaf-stalks are the catching and digestive organs.--Sarracenia, Darlingtonia.

NEPENTHACEÆ has only 1 genus, Nepenthes (the Pitcher-plant; about 35 species), especially found in tropical E. Asia; the majority are climbing shrubs. The leaf-stalks are twining organs, and terminate either simply in a tendril, or in addition to this, with a pitcher-shaped body (which in some species may be as much as a foot in length) on whose upper edge a lid-like structure is found (Fig. 420). In this pitcher, as among the Sarraceniaceæ, a fluid is secreted which is able to digest the animals captured (sometimes rather large) and which corresponds in some degree to the gastric juice.

Order 5. =Violaceæ (Violets).= The flowers are ☿, and generally zygomorphic, hypogynous, with S5, P5, A5, G3 (Fig. 421). The stamens are closely applied to the ovary, they have a very short filament, and at their summit generally a membranous appendage formed by the prolongation of the connective (Fig. 422 g). The ovary is unilocular with 3 parietal placentæ; style undivided (Fig. 422 B). The fruit is usually a 3-valved capsule, opening along the dorsal sutures (Fig. 423). Embryo straight; endosperm fleshy (Fig. 425).--Many are herbaceous plants (e.g. Viola), but in the Tropics shrubs are also found (e.g. Ionidium); a few are lianes; the leaves are scattered, with stipules, and involute in the bud.

Viola. The sepals are prolonged backwards beyond the point of insertion (appendiculate); the corolla is polypetalous, descending imbricate, and zygomorphic, its anterior petal being larger than the others and provided with a spur (Fig. 421). The 2 anterior of the 5 almost sessile stamens are provided with a spur-like nectary, which protrudes a considerable distance into the petaloid spur (Figs. 421, 422 n, sp). The style is club-like, and bears the stigma in a groove on the anterior side (Fig. 422 st). ~Herbs with rhizomes, or annuals; flowers solitary. V. odorata, canina, etc., have cleistogamic flowers which produce fruit in addition to the large, coloured (violet) flowers. The Pansy (V. tricolor) has large flowers adapted for insect-pollination, and also smaller, less conspicuous ones designed for self-pollination. The stigma, as in Fig. 422 A, st, and B, is situated on the anterior side of the stylar-head, immediately in front of the channel leading down to the spur (sp); below it is situated a valve, easily covered with pollen when the proboscis of an insect is introduced into the spur, but which closes upon its withdrawal; cross-pollination is thus secured.--The sweet-scented V. odorata is visited by the honey-bee, which insures cross-pollination, and in the absence of insect visits it effects self-fertilisation by cleistogamic flowers. The conspicuous but scentless V. tricolor, var. vulgaris, is less frequently visited by insects (humble-bees). In V. silvatica and V. canina the pollen is carried on the head or proboscis of the honey-sucking bee.--The fruits of V. odorata bury themselves slightly in the soil. In the others the fruits are raised above the ground; the 3 boat-shaped valves close together along the central line, and eject the seeds, one by one, with much violence, so that they are thrown to a great distance.~

FIG. 423.--Capsule after dehiscence (nat. size).

FIG. 424.--External view of the seed.

FIG. 425.--Seed in longitudinal section.]