2U TAKINQ UP OF POLLKN BY INSECTS. 



£er89, Dipsacese, and Caiyophyllacesa, which, owing to tlie assooiatioa of laiw 

 numbers of flowers in umbels, fascicles, spikes, or capitula, attbrd a pkjrgrouad 

 riclily furnished with slender waving- stamens wl\ere pollen is easily to be iiakeu 

 or bruslied off the anthers on every hand, although eaoli single blossom oal)' coa- 

 tains a few stamens. In tlie case, too, of tlie single flowers of Roses, Anemones, 

 Peonies, Poppies, Magnolias and Opuntias, whidi ai"© well supplied with sttimsns, 

 insects pushing between the anthers or feasting on poMoa that has dropped upoa 

 tlie petals g-et covered on head, tliorax, abdomen, wings, fmd leg's with tlie floury 

 pollen. This is true also of the spathes of Ai-oidea tuid of flg-inflorescenees wliidi 

 are haunted by midges, beetles, and gall-wtisps, and deposit tlieir pollen on time 

 visitors as they ci-awl out of their temporary refuge in tlie maunex- desoi-ibod on 

 pages 156-160. Mention was made in tliu same cliapter of the fact that iuseots, 

 after being imprisoned for a time in Uio flowers of tlio Amtoloohia, are quite 

 covered with pollen when they emerge. The phenomenon, whidi was there merely 

 glanced at, is so remarkable that it is worth while to give a somewhat fuller account 

 of it. In tlie widely-distributed species of Birtliwort represented in tig. 257 * on 

 p. 226, and named Aristoloohia Olematitis, the way into tlie enlarged base of the 

 flower is over a convenient ligulate alighting-place and tlirough a dai'k and ooni- 

 paratively narrow passage lined with hairs. The free extremities of these haira 

 point inwards, ie. towards the inflated oliambei-, and tliey permit visitors from tlie 

 insect-world — small black midges of the genera Oeratopogon and Ohwonovnus—io 

 pass into the chamber. But once inside, the midges aro obliged to reconcile tliem- 

 selves to remaining imprisoned for a couple of days. The haira, whilst offering no 

 hindrance to ingress present a bristling stockade of points to iuseots seeking to 

 escape (see fig. 267 "). At first the midges endure their captivity witli complacenoe, 

 for the warmth of their dungeon suits them, whilst the succulent cells lining its walls 

 afford a certain amount of nutriment. On tlie second or third day of imprisonment 

 the lateral walls of the anthers, which are adnate to the stigmatio column, open and 

 let the mealy pollen fall to the bottom of the chamber. The pollen is also aoosptaMe 

 to the midges for food, and they feast upon it liberally. At last, however, they 

 become restless and look for a means of exit, and in bustling actively about the 

 chamber, they cover their entire bodies with pollen. After this the hour of their 

 deliverance is no longer deferred. The hairs in the narrow passage wither and 

 collapse, leaving a free exit, and the midges all be-powdered with pollen hasten to 

 leave the flowers. That they retain no unpleasant recollection of their temporary 

 confinement may be inferred from the fact that they have no sooner escaped from 

 one flower than they creep into another, which has only just reached the stage at 

 which entrance becomes possible, This latter circumstance must bo emphasized in 

 order to arrive at a complete understanding of the significance of the curious phsno- 

 monon just described. The moment the flower is accessible to insects, the stigma 

 is ready to receive the pollen whilst the anthers are still closed. When the midges 

 proceed from an older to a younger flower, they brush against the latter's stigma, 

 which is situated right in front of the inner end of the dark passage, and deposit 



