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Studies in the Boraginaceae, XXVII. Some general observation on the Lithospermae

1954; Arnold Arboretum of Harvard University; Volume: 35; Issue: 2 Linguagem: Inglês

10.5962/bhl.part.8316

2474-3283

Ivan M Johnston,

Plant and Fungal Species Descriptions

In the previous papers of this series the genera composing the tribe Lithospermeae have been redescribed and individually discussed.Jour.Arnold Arb.34: 258-299 (1953) and 35: 1-81 (1954).The tribe having been surveyed, we are now prepared to present a new key to the twentythree genera concerned, and also some general observations concerning the tribe as a whole.Listed alphabetically the twenty-three genera of the Lithospermeae are as follows: Alkanna, Ancistrocarya, Arnebia, Buglos-soideSy Ccrinthe, Cystistemon (includes Vaupclia), Echioidcs, Echium, Halacsya, *Lasiarrhcnum, Lithodora, Lithospcrmum, Lobostemon, *il/acromcria, Maharanga, Moltkia, *Nomosa, Onosma, *Onosmodium, *Pcrittostcma, Podonosma, *Psilolacmus, and Stenosolenium.Six of the twentythree genera are endemic to America (those marked with the asterisk), and sixteen are endemic to the Old World.Only one genus, Lithospcrmum, has species present in both the Old and the New World.To be excluded from the Lithospermeae are a number of genera which at one time or another have been referred to it.These include Moritzia, Thaumatocaryon, Antiphytum, Amblynotopsis, Amphibologync, Sericostoma, Echiochilon, Megastoma, Myosotis, Mertcnsia, Trigonotis, Pulmonaria, Bothriospcrmum, Moltkiopsis, Mairetis and Neatostcma.Of these genera, Pulmonaria is best referred to the Anchuseae and Bothriospermum to the Cynoglosseae, and the remaining fourteen to the Eritricheae.As to habit the Lithospermeae are prevailingly herbaceous perennials.Species having only an annual duration are relatively few and occur only in Buglossoides, Arnebia, Stenosolenium, Cystistemon (including Vaupclia), Echium, and Cerinthe.The cymes are abundantly bracted and usually conspicuously so in all members of the tribe except Ancistrocarya, Floral dimorphy in several forms is present in five genera within the tribe.Heterostyly in a very elaborate form is present in Lithospcrmum % Echioides, and Arnebia, and in a simple form in Lithodora.Elsewhere among the Boraginoideae heterostyly is reported only among species of Inchusa and Pulmonaria of the Anchuseae, among Mertcnsia, Crypt ant ha, and Amsinckia in the Eritrichieae, and in one species of Paracaryum in the Cynoglosseae.Gvnodioecism is widespread within Echium.Outside the Lithospermeae it is known only in a few species of Myosotis and Lindclofia.Cleistogamy is developed in some species of Lit ho s permit m and elsewhere in the subfamily is known only in Neatostcma, Cryptantha and Pcctocarva.