272 OBSERVATIONS ON THE NATURAL FAMILY
In the mean time it may give some plausibility to the hypothesis to remark, that there are families of plants strictly natural in which a series of degradations exist, if I may so speak, from the assumed perfect pistillum, to a structure as simple as that of Compositae.
Thus in Protcacece we have the type of the perfect pis- tillum in the many-seeded folliculus of Embothrium ; the first degree of imperfection in that of Grevillea, where only one ovuhnn of each series remains ; a further reduction in the indehiscent monospermous fruit of Zeucospermum, in which the insertion of the ovulum is lateral ; and the sim- 9i] plest form in Protect itself, where the single ovulum is inserted at the base of the cavity. Proteaceae, however, exhibit a series of obliterations in the parts of a single pis- t ilium only. An illustration more in point, though some- what less perfect as a series, may be taken from Goodenovia, an order of plants very nearly related to the class of which we are treating. In the greater part of Goodenovia. the ovarium is bilocular, each cell having an indefinite number of seeds ; in the greater number of Sc<evolce, each cell is reduced to a single ovulum ; while in some species of the same genus, and in all the species of Dampiera, the ova- rium, though retaining its external characters, is reduced to a single monospermous cell, with an erect ovulum, as in Compositae. The natural order Crvciferce exhibits also obliterations, more obviously analogous to those assumed as taking place in syngenesious plants ; namely from a bilocular ovarium with two polyspermous parietal placentae, which is the usual structure of the order, to that of Isatis, where a single ovulum is pendulous from the apex of the unilocular ovarium. And lastly in the genus Bocconia, in the original species of which {B . frutescens) the insertion of the single erect ovulum has the same relation to its parietal placentae, as that of Compositae has to its filiform cords, a second species {B. cor data) exists in which these placentae are polyspermous.
My sixth observation on Compositae regards the order in which the florets expand. To understand the relation this order has to that of other families, it may be necessary first
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