[147]

Large leaf

[147]

Thalia

Left Hand

Smaller Leaf

[147v]

64 675

Chap. E 10

avellana)* (*Nature, 1875, p. 26), and what is more surprising with some few hermaphrodite plants as observed by H. Müller.*(* Die Befruchtung &c p. 285 & 339) These latter plants cannot fail to act on each other like dimorphic or trimorphic species, in which the union of two distinct individuals is necessary for full and normal fertility. With ordinary hermaphrodite species, the expansion of only a few flowers at the same time is one of the simplest means for favouring the intercrossing of distinct plants; but the presence of only a few open flowers will render them less conspicuous to insects, unless they are of large size, as in the case of several bulbous plants. Kerner thinks*(* Die Schutzmittel &c p. 23) that it is for this object that the Australian Villarsia parnassifolia produces daily only a single flower.

Dichogamy, which prevails so extensively throughout the vegetable kingdom, much increases the chance of distinct plants intercrossing. With proterandrous species, which are far more common than proterogynous, the