statements have been published during late years of the extraordinary tendency of hybrid plants to revert to their parent forms; but as it is not said how the flowers were protected from insects, it may be suspected that they were often fertilised with pollen brought from a distance from the parent-species.) The following case shows this in the clearest manner:  Gartner, before he had gained much experience, castrated and fertilised 520 flowers on various species with pollen of other genera or other species, but left them unprotected; for, as he says, he thought it a laughable idea that pollen should be brought from flowers of the same species, none of which grew nearer than between 500 and 600 yards. (10/16.  ‘Kenntniss der Befruchtung’ pages 539, 550, 575, 576.) The result was that 289 of these 520 flowers yielded no seed, or none that germinated; the seed of 29 flowers produced hybrids, such as might have been expected from the nature of the pollen employed; and lastly, the seed of the remaining 202 flowers produced perfectly pure plants, so that these flowers must have been fertilised by pollen brought by insects from a distance of between 500 and 600 yards. (10/17.  Henschel’s experiments quoted by Gartner ‘Kenntniss’ etc. page 574, which are worthless in all other respects, likewise show how largely flowers are intercrossed by insects.  He castrated many flowers on thirty-seven species, belonging to twenty-two genera, and put on their stigmas either no pollen, or pollen from distinct genera, yet they all seeded, and all the seedlings raised from them were of course pure.) It is of course possible that some of these 202 flowers might have been fertilised by pollen left accidentally in them when they were castrated; but to show how improbable this is, I may add that Gartner, during the next eighteen years, castrated no less than 8042 flowers and hybridised them in a closed room; and the seeds from only seventy of these, that is considerably less than 1 per cent, produced pure or unhybridised offspring. (10/18.  ‘Kenntniss’ etc. pages 555, 576.)

From the various facts now given, it is evident that most flowers are adapted in an admirable manner for cross-fertilisation.  Nevertheless, the greater number likewise present structures which are manifestly adapted, though not in so striking a manner, for self-fertilisation.  The chief of these is their hermaphrodite condition; that is, their including within the same corolla both the male and female reproductive organs.  These often stand close together and are mature at the same time; so that pollen from the same flower cannot fail to be deposited at the proper period on the stigma.  There are also various details of structure adapted for self-fertilisation. (10/19.  Hermann Muller ’Die Befruchtung’ etc. page 448.) Such structures are best shown in those curious cases discovered by Hermann Muller, in which a species exists under two forms,—­one bearing conspicuous flowers fitted for cross-fertilisation, and the other smaller flowers fitted for self-fertilisation, with many parts in the latter slightly modified for this special purpose. (10/20.  ‘Nature’ 1873 pages 44, 433.)