etc.; nor from the probability of the evil increasing after several generations, for on this latter head I have not sufficient evidence, owing to the manner in which my experiments were conducted.  But if plants bearing small and inconspicuous flowers were not occasionally intercrossed, and did not profit by the process, all their flowers would probably have been rendered cleistogene, as they would thus have largely benefited by having to produce only a small quantity of safely-protected pollen.  In coming to this conclusion, I have been guided by the frequency with which plants belonging to distinct orders have been rendered cleistogene.  But I can hear of no instance of a species with all its flowers rendered permanently cleistogene.  Leersia makes the nearest approach to this state; but as already stated, it has been known to produce perfect flowers in one part of Germany.  Some other plants of the cleistogene class, for instance Aspicarpa, have failed to produce perfect flowers during several years in a hothouse; but it does not follow that they would fail to do so in their native country, any more than with Vandellia, which with me produced only cleistogene flowers during certain years.  Plants belonging to this class commonly bear both kinds of flowers every season, and the perfect flowers of Viola canina yield fine capsules, but only when visited by bees.  We have also seen that the seedlings of Ononis minutissima, raised from the perfect flowers fertilised with pollen from another plant, were finer than those from self-fertilised flowers; and this was likewise the case to a certain extent with Vandellia.  As therefore no species which at one time bore small and inconspicuous flowers has had all its flowers rendered cleistogene, I must believe that plants now bearing small and inconspicuous flowers profit by their still remaining open, so as to be occasionally intercrossed by insects.  It has been one of the greatest oversights in my work that I did not experimentise on such flowers, owing to the difficulty of fertilising them, and to my not having seen the importance of the subject. (10/28.  Some of the species of Solanum would be good ones for such experiments, for they are said by Hermann Muller ‘Befruchtung’ page 434, to be unattractive to insects from not secreting nectar, not producing much pollen, and not being very conspicuous.  Hence probably it is that, according to Verlot ’Production des Varieties’ 1865 page 72, the varieties of “les aubergines et les tomates” (species of Solanum) do not intercross when they are cultivated near together; but it should be remembered that these are not endemic species.  On the other hand, the flowers of the common potato (S. tuberosum), though they do not secrete nectar Kurr ’Bedeutung der Nektarien’ 1833 page 40, yet cannot be considered as inconspicuous, and they are sometimes visited by diptera (Muller), and, as I have seen, by humble-bees.  Tinzmann (as quoted in ‘Gardeners’ Chronicle’ 1846 page 183, found that some of the varieties did not bear seed when fertilised with pollen from the same variety, but were fertile with that from another variety.)