form from the stamens to the pistil of corresponding length; and we shall presently see the importance of this adaptation. It must not, however, be supposed that the bees do not get more or less dusted all over with the several kinds of pollen; for this could be seen to occur with the green pollen from the longest stamens. Moreover a case will presently be given of a long-styled plant producing an abundance of capsules, though growing quite by itself, and the flowers must have been fertilised by their own kinds of pollen; but these capsules contained a very poor average of seed. Hence insects, and chiefly bees, act both as general carriers of pollen, and as special carriers of the right sort. Wirtgen remarks on the variability of this plant in the branching of the stem, in the length of the bracteae, size of the petals, and in several other characters. (4/4. ‘Verhand. des naturhist. Vereins fur Pr. Rheinl.’ 5 Jahrgang 1848 pages 11, 13.) The plants which grew in my garden had their leaves, which differed much in shape, arranged oppositely, alternately, or in whorls of three. In this latter case the stems were hexagonal; those of the other plants being quadrangular. But we are concerned chiefly, with the reproductive organs: the upward bending of the pistil is variable, and especially in the short-styled form, in which it is sometimes straight, sometimes slightly curved, but generally bent at right angles. The stigma of the long-styled pistil frequently has longer papillae or is rougher than that of the mid-styled, and the latter than that of the short-styled; but this character, though fixed and uniform in the two forms of Primula veris, etc., is here variable, for I have seen mid- styled stigmas rougher than those of the long-styled. (4/5. The plants which I observed grew in my garden, and probably varied rather more than those growing in a state of nature. H. Muller has described the stigmas of all three forms with great care, and he appears to have found the stigmatic papillae differing constantly in length and structure in the three forms, being longest in the long-styled form.) The degree to which the longest and mid-length stamens are graduated in length and have their ends upturned is variable; sometimes all are equally long. The colour of the green pollen in the longest stamens is variable, being sometimes pale greenish-yellow; in one short-styled plant it was almost white. The grains vary a little in size: I examined one short-styled plant with the grains from the mid-length and shortest anthers of the same size. We here see great variability in many important characters; and if any of these variations were of service to the plant, or were correlated with useful functional differences, the species is in that state in which natural selection might readily do much for its modification. ON THE POWER OF MUTUAL FERTILISATION BETWEEN THE THREE FORMS.