. British plants : their biology and ecology. Plants; Plant ecology. 160 BRITISH PLANTS weak stems. Some of the leaves bear tuberous buds (bulbils) in their axils, but they have the same struc- ture as the underground tubers. Subterranean leafy bulbils are found in Saxifraga granulata (the meadow- saxifrage), and these form the chief means of propa- gation. 5. Aerial Bulbils.—These are fleshy brood-buds which arise on aerial stems. The}7 become detached, fall to the ground, root, and grow into new plants. In the tiger-lily they develop in the axils of the lower leaves, and when the plant dies
. British plants : their biology and ecology. Plants; Plant ecology. 160 BRITISH PLANTS weak stems. Some of the leaves bear tuberous buds (bulbils) in their axils, but they have the same struc- ture as the underground tubers. Subterranean leafy bulbils are found in Saxifraga granulata (the meadow- saxifrage), and these form the chief means of propa- gation. 5. Aerial Bulbils.—These are fleshy brood-buds which arise on aerial stems. The}7 become detached, fall to the ground, root, and grow into new plants. In the tiger-lily they develop in the axils of the lower leaves, and when the plant dies they separate. In some species of onion— , Allium vineale—they replace some or all of the flowers. In very wet places, such as water-meadows, it is rare to find any flowers at all on the plant. In drier places, where the chances against the survival of the bulbils are increased, flowers are produced instead. 6. Viviparous Plants.—New plants sometimes appear on the most un- likely parts of plants, and almost any organ may, if the proper stimu- lation is present, become the seat of vegetative budding. Thus the leaves of Begonia become viviparous (Latin vivus, alive ; pario, I produce) if they are pegged to the ground and their veins slit across. Buds are formed adventitiously at the lower ends of the severed veins. From these buds little plants arise, which, if separated, take root easily in the soil and grow. Similar plantlets are formed on the radical leaves of the cuckoo-flower (Cardamine pratensis) when growing in wet, fertile meadows (Fig. 64). In many alpine grasses —, Poa alpina and Festuca ovina—the flowers become transformed into plantlets (Fig. 65). The stimulation in al It hese cases is produced by the accumulation of excess of nutritive material at certain points. In the Begonia the retreat of the sap down the leaf is stopped at the points where the veins are severed and the buds arise. In the alpine grasses flowers are not produced because of the.
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