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Show DIGITALIS PURPUREA. CHAr. III. 82 . h h '1st in search of nectar, carry tbc larger huinble-bees, whw ' w ~he two upper and longer po llcn from flowe. r to !lfelno wbeer.f ore the two lower and 0 shl orter stanlens shed th~u po . fact probably is, as Dr. g e re- . ones. The meamng of this he longer stamens stand near to Inarks * that the an thcrs of 1~ b the most likely to fertilise l t; the sti~ma, so that they wou e.d self-fertilisation, they shed c1 ntagc to avm . h . and as it is an a va . 0' the chance. There I.s' ow~ver , their pollen first, thus les~;~I~'?lisatiOn until the bifid stigma but little danger of s~ - e~ \hat pollen placed on the stJgma opens. for Hildebrandt oun d effect The anthers, whwh before' it had opened produce nlo with ~espect to the tubular arc large, stanc 1 a t first traton sdveehrissec eY i n this posi· t w· n the y wo uld ' corolla and if they were . th pollen the whole back and as Dr. Ogle also remarks, s~e': Wiin a useless manner; but the sides of an entering hum 1 e- et~emselves longitudinally before anthers twist round and p acde . ner side of the mouth of the they dehi·s c~. The lowde rw aitnh h1a11i rs, and these col 1e c t so mu ch corolla is thwkly clothe I have seen the under surface of a of the fallen pollen thatd with it; but this can never be aphumble- bce thickly duste . treating do not turn then t. as the bees In re tl plied to the s Igma, I was therefore puzzled whether .'ese under surfaces upwards. t M Belt has I think, explamcd hairs were of any use ; . b~ . fr bees are ~ot fitted to fertilise their use: the smaller kin s ~I wed to enter easily they would the flowers, and if the~;e:e~:r o large bees would haunt the steal much nectar, a l . t the dependent flowers flowers. Humble-bees ca~ cra;e I~ :airs as footholds while with the greatest ease, using 11 bees are impeded by h . but the sma er h sucking the oney '. t len th struggled through them, t ey them, and when, having a .. g b they are completely l. y preCipiCe a ove, d . . reach the s Ipper h t heel many flowers urmg baffied." Mr. Belt says that e wade " ly once saw a small a whole season I· n North Wha les ' an wereo ns een trying in vam· to bee reach the nectary' thoug many d o so. " ++ . in its native SO'll I. n N or th Wales I covered a plant growing l 'th its own pollen, with a net, and fertilised six flowers eac 1 WI * 'Popular Science Review,' .Tan. 1870, P· 50. h ·1 t 'Geschlechter -Vert el ung bei den Pfianzen,' ~867., P· 2,0 .. ++ 'The Naturalist m NICara ·, ,.., 132 But it appears gua, HIS {J:.ficJr ('Die Defruchtung from . u 285\ that der Blumen,' 1873, .P· . );ccecd small insects sometimes st in entering the flower s. CHAP. III. CROSSED AND SELF-FERTILISED PLANTS. 83 and six others with pollen from a distinct plant growing within the distance of a few feet. The covered plant was occasionally shaken with violence, so as to imitate the effects of a gale of wind, and thus to facilitate as far as possible self-fertilisation. It bore ninety-two flowers (besides the dozen artificially fertilised), and of those only twenty-four produced capsules; whereas almost all the flowers on the surrounding uncovered plants were fruitful. Of the twenty-four spontaneously self-fertilised capsules, only two contained their full complement of seed ; six contained a moderate supply; and the remaining sixteen extremely few seeds. A little poUen adhering to the anthers after they had dehisced, and accidentally falling on the stigma when mature, must have been the means by which the above twentyfour fiowm·s were partially self-fertilised; for the margins of the corolla in withering do not curl inwards, nor do the flowers in dropping off turn round on their axes, so as to bring the pollencovered hairs, with which the lower surface is clothed, into contact with the stigma-by either of which means self-fertilisation might be effected. Seeds from the above crossed and self-fertilised capsules, after germinating on bare sand, were plan ted in pairs on the opposite sides of five moderately-sized pots, which were kept in the greenhouse. The plants after a time appeared starved, and were therefore, without being disturbed, turned out of their pots, and planted in the open ground in two close pamllel rows. They were thus subjected to tolerably severe competition with one another; but not nearly so severe as if they had been left in the pots. At the time when they were turned out, their leaves were between 5 and 8 inches in length, and the longest leaf on the finest plant on each side of each pot was measured, with the result that the leaves of the crossed plants exceeded, on an average, those of the self- fertilised plants hy · 4 of an inch. In the following summei· the tallest fiower-steru on each plant, When fully grown, was measured. There were seventeen crossed plants; but one did not produce a flower-stem. There were also, originally, seventeen self-fertilised plants, but these had such poor constitutions that no less than nine died in the course of the winter and spring, leaving only eight to be measured, as in the following table:- G 2 |