. The origin of floral structures : through insect and other agencies. Plants; Flowers; Flowers. 126 THE STKUCTUEE OF FLOWERS,. has to support its own weight, as will be easily understood from what has been described, and by referring to the diagram (Fig. 40a). If the tissue does not remain firm nnder pressure, then the lever-action of a spring may fail to be secured, and the organ will oscillate freely, as on a pivot. This I take to be another result of a constant, but of course unconscions, effort of the insect Fig. of deciinate to P^^h the Organ in a Certain direc- S"of f
. The origin of floral structures : through insect and other agencies. Plants; Flowers; Flowers. 126 THE STKUCTUEE OF FLOWERS,. has to support its own weight, as will be easily understood from what has been described, and by referring to the diagram (Fig. 40a). If the tissue does not remain firm nnder pressure, then the lever-action of a spring may fail to be secured, and the organ will oscillate freely, as on a pivot. This I take to be another result of a constant, but of course unconscions, effort of the insect Fig. of deciinate to P^^h the Organ in a Certain direc- S"of fOTccs"""'^ "" *'""â tion- It 'S thus that anthers become versatile, and oscillate, and may become even inverted in position, when pollination is being effected by insects. Consequently anthers normally introrse can be made to assume a pseudo-extrorse position. This happens with some Cruciferm as Cardamine pratensis, Tulips, etc. A similar cause I would attribute to the formation of the oscillating anthers of Salvia, and of the species of Calceolaria, as G. Pavonii, which form the section Aposecos of that genus, as shown m Fig. 32, a, p. 109. As an example of an entire flower illus- trating the distribution of forces, the accom- panying figure of Lamium album (Fig. 406) will explain how the forms of the calyx and corolla are adjusted to bear the weight of the insect. The bee alights on the lip and then partially crawls into the expanded mouth of the corolla, so that its weight now lies in the direction of w. The fulcrum will be at /, and the resultant of these is in the opposite direction to r. This is where the strain will be felt; so that it is just at this. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Henslow, George, 1835-1925. New York : Appleton
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Keywords: ., bookcentury1800, bookdecad, booksubjectflowers, booksubjectplants
