Flowers for the garden
Umbellifers
Umbelliferae
The family Umbellifers is among the largest and most economically important families of flowering plants. It includes about 300 genera and 3,000 species, distributed across almost all the land surface of the globe. However, Umbellifers are most numerous in the warm-temperate and subtropical regions of the Northern Hemisphere, while in tropical countries they are mainly confined to mountainous areas.
However, among Umbellifers there are species that form dense (Azorella), as well as dwarf stemless or nearly stemless annuals, for example Hohenackeria exscapa, which occurs in the semi-desert regions of Transcaucasia. In the stems, as in all other organs of Umbellifers, there are secretory canals containing essential oils and resinous substances that give them their characteristic scent. Leaves of Umbellifers are usually alternate, without stipules, and are divided into a deeply dissected blade (often with filiform segments), a petiole and a sheath that clasps the stem. However, there are quite a few exceptions in this respect. Thus, in numerous species of the genus Bupleurum the leaves are entire and entire-margined without sheaths and usually with parallel or arcuate venation. Their shape ranges from narrowly linear to cordate and almost round, and in some species the upper leaves may even be perfoliate. It was previously assumed that Bupleurum leaves represent blade-like broadened petioles, but anatomical and morphological studies did not confirm this assumption. Complete reduction of leaf blades to a filiform midrib occurs among Umbellifers only in species of Lilaeopsis — creeping marsh plants distributed in America, Australia and New Zealand.
Entire but toothed-margined leaf blades occur in many tribes of Umbellifers. In species of Hydrocotyle they are almost rounded and are borne on long petioles, and in the only European species of this genus — Hydrocotyle vulgaris)) — the leaves are even peltate. In this genus, as in other genera of the more primitive subfamily Hydrocotyloideae, small stipules occur at the base of the petioles, which are absent in other Umbellifers. Another rare exception — opposite leaf arrangement — occurs in species of two small American genera: Bowlesia and Spananthe, as well as in the Canary Islands endemic Drusa oppositifolia. Very small, densely arranged, often entire and entire-margined leaves occur in Azorella and some other high-mountain Umbellifers of South America. Often two-rowed, spiny-toothed at the margin, lanceolate or linear leaves of some species of Eryngium and of the Australo–New Zealand genus Aciphylla resemble the leaves of Bromeliaceae or some Agave species. Less original are species of the South American campos (savanna-like vegetation) — Eryngium junceum and Eryngium eriophorum with rigid narrow-linear leaves up to 80 cm long and 5 mm wide, as well as Eryngium pseudojunceum from Chile, which has hollow narrow-linear leaves with transverse partitions, as in many Juncus species. Strongly fleshy leaves occur in several species of Eryngium and in some other, usually halophilous, genera, for example the Mediterranean littoral genus Crithmum, known in Crimea and the Caucasus.