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Show 96 HETEROSTYLED DIMORPHIC PLANTS. CnAP. III. by the ring of broad filame~ts, .and would neve~ have received any pollen. As It IS, the styles. diverge and pass out between the fi~ame~.t~. After this move- 1nent the short stig1nas he within th~ tube of the corolla; and their papillous surfaces being now tur~ed upwards are necessarily brushe.d by every entenng insect and thus receive the required pollen. In 'the long-sty led form of L. grandiflorum, the almost parallel or slightly diverging anthers and stigmas project a little above the tube of the somewhat concave flower; and they stand directly over the open space leadin()' to the drops of nectar. Consequently when insectsb visit the flowers of either fonn (for the stamens in this species occupy the same positio~ in both forms), they will get their foreheads or probosCides well dusted with the coherent pollen. As soon as they visit the flowers of the long-styled form they will necessarily leave pollen on the proper surface of the elongated stigmas; and when they visit the shortstyled flowers, they will leave pollen on the upturned stigmatic surfaces. Thus the stigmas of both fonns will receive indifferently the pollen of both forms; but we know that the pollen alone of the opposite form causes fertilisation. In the case of L. perenne, affairs are arranged more perfectly; for the stamens in the two forms stand at different heights, so that pollen from the anthers of the longer stamens will adhere to one part of an insect's body, and will afterwards be brushed off by the rough stigmas of the longer pistils ; whilst pollen from the anthers of the shorter stamens will adhere to a different part of the insect's body, and will afterwards be brushed off by the stigmas of the shorter pistils ; and this is what is required for the legitimate fertilisation of both forms. The corolla of L. perenne is more CHAP. III. LINUM PERENNE. 97 expanded than that of L. grandijlorum, and the stigmas of the long-styled form do not diverge greatly from one another; nor do the stamens of either form. Hence insects, especially rather small ones, will not insert their proboscides between the stigmas of the long-styled form, nor between the anthers of either form (Fig. 5), but will strike against them, at nearly right angles, with the backs of their head or thorax. Now, in the long-sty led flowers, if each stigma did Fig. 5. Long-styled form of L. PERENNE, var. Austriacum in its early condition before the stigmas have rotated. The petals and calyx have been removed on the near side.* not rotate on its axis, insects in visiting them would strike their heads against the backs of the stigmas; as it is, they strike against that surface which is covered * I neglected to get drawings made from fresh flowers of the two forms. But Mr. Fitch has made the above sketch of a long-sty led flower from dried specimens and from published engravings. His well-known skill ensures accuracy in the proportional size of the parts. H |