Asteraceae:
tribe Cichorieae
Cichorium intybus (Common Chicory, Wild Succory)
The tribe Cichorieae includes a diverse range of related genera of the Asteraceae (Daisy Family) that may appear at first to have little in common. However, their flowers are similar in form, with all the florets having both male and female functional parts and having the petal-tube drawn-out into a strapshaped ligula (i.e. ligulate florets) usually with 5 teeth at the tip (indicating that all five petals contribute to their formation). Sometimes their general growth forms are similar too. They produce milky-white latex. Latex is a special fluid or sap produced by cells called laticifers and in the Asteraceae these form continuous tubes carrying the latex. (Latex sap is separate from xylem sap and phloem sap). The latex is stored under pressure and when a latex vessel is cut it rapidly oozes out and congeals. Latex is thought to have a protective function, protecting wounds from infection and deterring herbivores. Some of the better known genera in this tribe include:
Crepis (hawksbeards), Hieracium (Hawkweeds), Pilosella (Hawkweeds), Sonchus (Sow-thistles), Picris, Lapsana (Nippleworts), some of which are covered here.
Tragopogon - covered here.
Leontodon (Hawkbits), Cicerbita, Cichorium (Chicories) and Lactuca (Lettuces), the subjects of this page.
The ligules twist, bend and flutter in a light breeze.
Chicory (Wild Succory), Cichorium intybus, is a perennial with a large, tapering and fleshy root and an erect stem brnaching in a paniculate manner (like a panicle, that is with branches on either side of a central axis). The stem is usually 30 to 120 cm in height.
The capitulum above is in the fruiting stage. The fruit are characteristic of Asteraceae: a layer of dry single-seeded achenes (cypselas). The surrounding phyllaries (bracts that form the involucre or cup below each flower head) have opened widely to allow fruit dispersal in the capitulum above. Each achene, however, lacks a feathery pappus for wind dispersal and the pappus is instead reduced to a circle of short scales with a fringe-like (fimbriated) margin around the top of each achene, as can be seen here. The mode of dispersal is not obvious as the achenes have no obvious device to assist wind or animal dispersal, but perhaps vibrations of the stem scatters the achenes. I speculate that the reduced pappus, if capable of any movement upon drying out, may serve to help separate and liberate the individual achenes. Plants do not always aim to scatter their seeds as far as possible, in fact most plants scatter most of their seeds just a short distance away from the parent plant where conditions are likely to be suitable, sustaining the population and allowing its gradual expansion.
As a typical member of the Asteraceae, the 'flower' above is really a compound head or capitulum of tiny florets. The petal tube of each floret (flower proper) is extended into a strapshaped ligule (petal-like structure). The ligules often have 5 teeth at the apex, showing that it is a structure formed by all 5 fused petals (though sometimes only 4 teeth may be apparent). Sometimes the capitulum is considered as a condensed inflorescence, in which case the stalk bearing it is a peduncle (inflorescence stalk) rather than a pedicel (individual flower stalk).
As can be seen above, there is a main upright stem emerging from the perennial rootstock. Note the paniculate branching sending out wandlike ascending branches, alternating from side-to-side and emerging from the stem at a wide angle (spreading). We therefore have a compound inflorescence: a panicle of capitula. As plants evolve they are adept at changing the nature and relationships of the standard flowering plant parts, such that we quickly run out of unambiguous names for the structures we see! The root is large, tapering and fleshy. Short woolly hairs clothe the stem (below).
The radical leaves (lowermost leaves emerging directly from the rootstock) are variable in contour, more-or-less entire (undivided) or incised into lobes. Cultivated varieties often have entire basal leaves. The lowermost leaves may have a wavy margin and may be divided into lobes which may point backwards (as in a dandelion leaf). Upper stem leaves are lanceolate (shaped like a lance head) and have a pair of basal lobes or auricles that partially wrap around the stem.
The anthodes (flowering nodes or cpaitula) are quite numerous and occur either singly at the ends of the main peduncles, or in groups of 2 or 3 in the axils of upper stem leaves (bracts).
The basal leaves, including the radical leaves shooting directly from the rootstock and the lowermost stem leaves (cauline leaves), are variously incised and may be runcinate (with tooth-like lobes pointing to wards the base) like the leaves in a typical Dandelion (Taraxacum).
The ligules vary in color from bright blue to white. Each compound flower is about 2.5 to 3 cm in diameter. Cultivars have been grown as root crops (the roots being cooked and eaten like parsnips) and as leaves for salads (the wild types have bitter tasting leaves). Forcing varieties are grown in darkness to produce white shoots (chicons) as food. Cichorium intybus grows on roadsides, field-borders, banks and on waste ground, especially on chalk. It is native to most of Europe and North Africa and countries around the Caspian Sea.
Lactuca (Lettuces)
Above: a capitulum of Lactuca virosa, Great Lettuce, a species of wild lettuce. It is native to western Europe and parts of northwest Africa. It is a biennial and produces a flowering stem that may reach 200 cm or more in height, but is often much shorter.
The capitulum is quite small, but rather exquisite, and consists of only 10 to 15 florets, each with a pale yellow ligule (with a central bronze-colored stripe on the underside of each ligule, at least in this specimen) which may be streaked violet. The flowers/capitula close by noon (by 11:30 am they were almost fully closed, but are seen here at 10:30 am). Additionally, only a few open each day (at least at any one time) and most plants in the area had none open at this time, so observing the flowers in their full glory can be a bit of a challenge.
Note the bronze stripes on the underside (backs) of the ligules, visible in the capitulum that is already largely closed.
Lactuca virosa produces a clear latex that latter turns milky white when flowering takes place and then has the characteristic odor of opium.
The capitula are arranged in a panicle, rather as in Cichorium, but with more and smaller capitula. The purplish tinge is not uncommon in Lactuca virosa. The stem bears prickles, sometimes over most of its length, but more so at the base. In fruit, the phyllaries (bracts or scale-leaves) enclosing the capitulum (forming the cup or involucre) open out (presumably only in dry conditions) to allow the achenes to disperse.
Above: the involucre (basal cup) of this fruiting capitulum is opening wide, but the pappi (singular: pappus) of whitish hairs, borne on the end of a beak, have not yet opened out. Once open, they remain open in the afternoon long after the flowering anthodes have closed. It is possible that they can reclose in damp weather, I have not checked this.
Above: heads of achenes with their pappi opened out, exquisite structures resembling but much smaller than a dandelion 'clock'. The black achenes are diagnostic of L. virosa. In the related species L. serriola, the achenes are pale-grey or tan-colored and have a tuft of additional hairs at the base of the beak. The beak presumably has an aerodynamic function, perhaps creating space for lift-generating vortices to form beneath the pappus. The pappus hairs and beaks are deciduous, soon falling off once dispersal has been affected.
Above: a lower stem leaf of Lactuca virosa, note the two rounded basal lobes or auricles. These are pressed to the stem and in the lower stem leaves they are bent down parallel to the stem as here. This is a characteristic of L. virosa.
Note the predominant alignment of the leaves and panicle of capitula to intercept the sun (for photosynthesis in the former and for display to pollinators for the latter).
Some of the Lactuca plants in this population were much shorter and some of them, both tall and short lacked the purple tinge. Some of these could be the related Lactuca serriola (formerly Lactuca scariola, Prickly Lettuce) which tends to be annual and is more widely distributed over much of Europe, North Africa and parts of Asia. It is thought that food cultivars of lettuce were derived from Lactuca serriola. It is apparently not uncommon to find both species growing together. Although there are differences between the two in terms of leaves and stems they are perhaps most easily distinguished by their achenes.
Note the flower buds on the axillary branches growing out of the leaf axils.
Some of the leaves twist their blade into a vertical position. The vertical leaves are said to align north-south (unless they are pointing straight up), presumably to intercept the sunlight from east-west and the panicles seem to also face east-west. This phenomenon has been noted in L. serriola, but perhaps occurs in both species. I have not rigorously verified this, but the plants in this population did seem to have similar orientations to one another. This could be an interesting study.
Spines along the midribs occur in both L. virosa and L. serriola.
We have seen that Cichorium and Lactuca do indeed have certain similarities: capitula with florets all ligulate (possessing ligules) and the paniculate arrangement of the capitula around a main stem. Both occurred at the same site. However, there are interesting differences we have to consider: Lactuca closes its flowers by noon, Cichorium does not (but presumably closes its flowers at night as most Asteraceae do), the differences in ligule color and flower size, which presumably influence attractiveness to different pollinators. Lactuca virosa is often a much taller plant, investing in a towering inflorescence, perhaps compensating for its lack of showy flowers in attracting pollinators. There are differences in seed dispersal, with the achenes of Lactuca being wind-dispersed and there are differences in the chemical constituents of the latex. A comparison of Cichorium and Lactuca could be a fruitful study.