Page:Popular Science Monthly Volume 45.djvu/806



HILE the vegetative organs of barberries exhibit, as we have seen, an abundant variety of form and many degrees of differentiation, the reproductive organs are, on the contrary, so very similar throughout the group that what we may find to be true of a single example, such as Berberis vulgaris, will apply very generally to all the other species.

In the flowers (Figs. 2 and 3) there is traceable in almost every feature some relation to the visits of insects. Thus the conspicuousness gained by the yellow color of every part, enhanced by the clustering of the flowers and supplemented by their sweet perfumes attractively advertise, the abundant nectar which visitors find provided for them through the activity of the twelve orange glands (Fig. 3, N). In time of rain these sweets are protected by the pendent or nodding attitude of the flowers. On the arrival of an insect the movements by which it obtains a sip of the nectar are turned to account in a way to secure an advantageous transfer of the pollen from anther to stigma.

It has long been known that the stamens are so sensitive that at the slightest touch on the filament there is a quick inward bending of the organ which brings the anther with its exposed pollen to the center of the flower. Subsequently the stamen regains its original position, and will now respond to another touch as before. Sprengel in whose classic work were first revealed some of Nature's most cherished secrets, considered this to be an arrangement whereby insect visitors brought about the self-pollination of the flower, thus making possible the setting of seeds. But later experiments have shown that while Sprengel was entirely right in supposing insect visits to be of the utmost importance in securing fertilization, nevertheless the barberry is no exception to the general rule announced by Darwin, that flowers which attract insects gain from their visits the advantages which come from the transference of the pollen of one flower