. The natural history of plants, their forms, growth, reproduction, and distribution;. Botany. DISPERSAL BY WIND. 855 When quite dry, these envelopes are extremely thin and delicate, and sometimes their weight is still further reduced by a portion of the tissue being torn during desiccation, in which case the whole assumes a sieve-like or latticed appearance. The small fruit within the envelope defines the position of the centre of gravity, and consequently determines also the attitude of the structure as a whole that best adapts it to dispersion by the wind. In several Papilionacese, as in Ca
. The natural history of plants, their forms, growth, reproduction, and distribution;. Botany. DISPERSAL BY WIND. 855 When quite dry, these envelopes are extremely thin and delicate, and sometimes their weight is still further reduced by a portion of the tissue being torn during desiccation, in which case the whole assumes a sieve-like or latticed appearance. The small fruit within the envelope defines the position of the centre of gravity, and consequently determines also the attitude of the structure as a whole that best adapts it to dispersion by the wind. In several Papilionacese, as in Callipeltis cucullata and the yellow-flowered species of Clover ( Trifolium agrarium and T. badium; see figs. 469 L 2. s, )_ the dried petals of the corolla are fashioned into an envelope which incloses the small 1-seeded legume, and in several species of Lady's Fingers ( Anthyllis tetraphylla and A. Vulneraria; see figs. 464^. Kg. 469.—Dispersion of fruits and seeds by the wind. Trifoliwrn badiuTn. — i Inflorescence. 2 Same with fruit ripened, s Flower. * Fruit enveloped in the dried petals. 6 Longitudinal section through the fruit in its envelope of petals.—Vertieordia oculata. « Fruit. 1 Longitudinal section through the fruit, s Five " feathers " from the fruit, s, *, s, and s magnified. and 464 2), and some species of Clover of the tribe Vesicastrum ( Trifolium fragifenom and T. tomentosum; see figs. 464' and 464*), the inflated calyx plays the same part. In many Labiates also ( Galaminta, Salvia, Thymus), the calyx is converted into a dry, saccate envelope, which is severed from its stalk by any external stimulus, and then serves as a means of dispersing the ripe nutlets con- tained in it. In the Hop-hornbeam (Ostrya, see figs. 464 ^ and 464''), the small nut is enveloped in the sac-like bract; and in many Grasses, as, for instance, Briza maxima and Melica altissima (see figs. 468 * and 468 ^j, the dry glumes constitute a covering to the s
Size: 2113px × 1182px
Photo credit: © The Book Worm / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1800, bookdecade1890, booksubjectbotany, bookyear1895
