It has now been shown that nine of the species in this genus exist under two forms, which differ not only in structure but in function. Besides these Mr. Scott enumerates 27 other species which are heterostyled (1/13. H. Muller has given in ‘Nature’ December 10, 1874 page 110, a drawing of one of these species, viz. The alpine P. villosa, and shows that it is fertilised exclusively by Lepidoptera.); and to these probably others will be hereafter added. Nevertheless, some species are homostyled; that is, they exist only under a single form; but much caution is necessary on this head, as several species when cultivated are apt to become equal-styled. Mr. Scott believes that P. Scotica, verticillata, a variety of Sibirica, elata, mollis, and longiflora, are truly homostyled; and to these may be added, according to Axell, P. stricta. (1/14. Koch was aware that this species was homostyled: see “Treviranus uber Dichogamie nach Sprengel und Darwin” ‘Botanische Zeitung’ January 2, 1863 page 4.) Mr. Scott experimented on P. Scotica, mollis, and verticillata, and found that their flowers yielded an abundance of seeds when fertilised with their own pollen. This shows that they are not heterostyled in function. P. Scotica is, however, only moderately fertile when insects are excluded, but this depends merely on the coherent pollen not readily falling on the stigma without their aid. Mr. Scott also found that the capsules of P. verticillata contained rather more seed when the flowers were fertilised with pollen from a distinct plant than when with their own pollen; and from this fact he infers that they are sub- heterostyled in function, though not in structure. But there is no evidence that two sets of individuals exist, which differ slightly in function and are adapted for reciprocal fertilisation; and this is the essence of heterostylism. The mere fact of a plant being more fertile with pollen from a distinct individual than with its own pollen, is common to very many species, as I have shown in my work ‘On the Effects of Cross and Self-fertilisation.’ Hottonia palustris.