Page:EB1911 - Volume 22.djvu/913

Rh

The order falls into several well-defined tribes which are distinguished by characters of the flower and fruit; all are

From Strasburger's Lehr- "J

bud! der Bofanik, by per- A

mission of Gustav Fischer.

FIG. 2.-Ranunculus

FIG. 3.~Single FIG. 4.-Fruit of Colarvensis. Carpel in follicle show- umbine (Aguilegia) longitudinal section. ingdehiscence formed of five fol(After Baillon, en- by the ventral licles. larged.) suture.

represented among British native or commonly grown garden plants.

Tribe I. Paermieae, peony group, are mostly herbs with deeply cut leaves and large solitary showy flowers in which the parts are spirally arranged, the sepals, generally five in number, passing gradually into the large coloured petals. The indefinite stamens are succeeded by 2-5 free carpels which bear a double row of ovules along the ventral suture. Honey is secreted by a ring-like swelling round the base of the carpels, which become fleshy or leathery in the fruit and dehisce along the ventral suture. There are only three genera, the largest of which, Paeonia, occurs in Europe, temperate Asia and western North America. P. o #icinali.r is the common eony.

P Tribe II. Helleboreae are almost exclusively north temperate or subarctic; there are 15 genera, several of which are represented in the British flora. The plants are herbs, either annual, e.g. Nigella (love-in-a-mist), or perennial by means of a rhizome, as in Aconitum or Eranthis (winter aconite). The' leaves are simple, as in Callha, but 'more often palmately divided as in hellebore (fig. 6), aconite (fig. 5) and larkspur. The flowers are solitary (Eranlhis) or in e. 45

Q li   /

FIG. 5.-Five-partite leaf FIG. 6.-Pedate leaf of StinkingHellebore (Helleborus foetidus). It is a

palmately-partite leaf, in which the lateral lobes are deeply divided. When the leaf hangs down it resembles the foot of a bird, and hence

the name.

of Aconite.

cymes or racemes, and are generally regular as in Caltha (king-cup, marsh marigold), Trollius (globe-flower), Helleborus, Aquilegia. (columbine); sometimes medianly zygomor hic as in Aconitum (monkshood, aconite) and Delphinium (larlispur). 'The-carpels, generally 3 to 5 in number, form in the fruit a many-seeded follicle, except in Actaea (bane berry), where the single carpel develops to form a many-seeded berry, and in Nigella, where the five carpels unite to form a five-chambered ovary. There is considerable variety in the form of the floral envelopes and the arrangement of the parts. The outer series, or sepals, generally five in number, is generally white or bright-coloured, serving as an attraction for insects, especially bees, as well as a protection for the rest of the flower. Thus in Caltha and Trollius the sepals form a brilliant golden-yello w cup or globe, and in Enmlhis a pale yellow star which contrasts with the green involucre of bracts immediately below it; in Nigella thee' are blue or yellow, and also coloured in Aquilegia. In Hellebore the greenish sepals persist till the fruit is ripe. Aconitum and Delphznium differ in the irregular development of the sepals, the posterior sepal being distinguished from the remaining four by its helmet-shape (Aconitum) or spur (Delphinium). In Caltha there are no petals, but in the other genera there are honey-secreting and storing structures varying in number and in form in the different genera. In Trollius they are long and narrow with a honey-secreting pit at the base, in Nigella and Helleborus (fig. 7) they form shortnx K I, A - iv x 4;

W, '~ M, ¢», ,

W, Q ss;

e    I

if'  § ' ll|'l'|', l|,

"r';, l'il ' *NA

Q W, ill


 * '| .x M

1  “ I

2 1

FIG. 7.-Helleborus niger. I, vertical section of flower; 2, nectary, side and front view (nat. size). stalked pitchers, in Aquilegia they are large and coloured with a showy petal-like upper portion and a long basal spur in the tip of which is the nectary. In Delphinium they are also spurred, and in Acomtum form a spur-like sac on a long stalk (fig. 8). The parts ~»» of the Hower are generally

arranged in a

1' . spiral (acyclic), but are

sometimes hemicyclic,

the perianth forming

a whorl as in winter

V*



0 F aconite; rarely is the

, 1

,



l

e= ~

flower cyclic, as in

Aguilegia (fig. 9) where

)-§ '


 * "" lm' - '   o


 * ~;'2— s'. 'lip

='¥+1*?¢,    -. °°°°f

esta.

ff-' if

FIG. 8.-Part of the flower of Aconite FIG. 9.-Floral dia(Aconilum Napellus), showing two

irregular horn-like petals p, supported on grooved stalks o. These serve as nectarines. s, the whorl of stamens inserted on the thalamus, and surrounding the pistil.

the parts throughout are arranged in alternating whorls. In Callha, where there are no petals, honey is secreted by two shallow depressions on the side of each carpel.

Tribe III. Anemoneae, with 8 genera, are chiefly north temperate, arctic and alpine plants, but also pass beyond the tropics to the southern hemisphere. They differ from the two preceding tribes in the numerous carpels, each with only one ovule, forming a fruit of numerous achenes. They are annual or perennial herbs, erect as in Anemone, Thalictrum (meadow-rue) and many buttercups, or creeping as in Ranunculus repens; the section Balrachium of the genus Ranunculus (g.v.) contains aquatic plants with submerged or floating stems and leaves. The flowers are solitary, as in Anemone Pulsalilla (Pasque flower) and the wood aneirone, or cymose as in species of Ranunculus, or in racemes or panicles as in Thaliclrum. The parts are spirally arranged throughout as in IM)/05747743 (m0US€'fall), where the very numerous carpels are borne on a much elongated receptacle, or Adonis (pheasant's eye), or the 1Z'€f13U§ h IS Wh0fl@d as in Anemone and Ranunculus. In Anemone there is a whorl of foliage leaves below the flower, as in Eranthis. In Anemaize and Thnlic/rum there is only one series of perianth leaves, WhlCh are petaloid and attractive in Anemone where honey is secreted by modified stamens, as in A. Pulsalilla, or, as in A. 'nemorgsa (Wood anemone), there is no honey and the flower is visited by insects for the sakeof the pollen; in Thaliclrum the perianth is greenish or gram of Columbine

(Aquilegia) showing

regular cyclic arrangement.