H. F. Wernham. 
150 
are hemi-parasites. This tendency is expressed in two allied families, 
each of which is extremely specialized in habit—the insectivorous 
Lentibulariaceae on the one hand, and the totally parasitic Oroban- 
chaceae on the other. 
The Lentibulariaceae reflect a high degree of advance in floral 
characters. The corolla is usually strongly zygomorphic, often 
personate, and with a spur more or less prominently developed. 
The conspicuous bilabiate stigma is highly specialized ; and the 
numerous ovules are borne on a free-central placenta. The last- 
named character, as Bentham 1 has pointed out, is foreshadowed in 
Scrophulariaceae. He says: “ In respect of the former character 
“ (free-central placentation) they (Lentibulariaceae) come very 
“ near to Limosella, Lindernia, and other Gratioleas, with parallel 
“ dissepiments and entire valves ; for in these plants the dissepi- 
“ ment is very thin, and usually detaches itself from the valves 
“ before maturity, so that being concealed by the seeds, which fill 
“ nearly the whole capsule, it often escapes observation, and many 
“ of these genera have frequently been described as having a 
“ unilocular fruit.” The unilocular character of the ovary in Len¬ 
tibulariaceae, then, would appear to be secondary, the result in 
descent of the degradation of an ancestral septum. 
In Orobanchaceae the androecium consists of four stamens 
arranged didynamously. The habit represents the final stage of 
the parasitic tendency exhibited in Rhinanthoideae. The most 
important difference between Orobanchaceae and Scrophulariaceae 
is in the septation of the ovary; in the former family the ovary 
is unilocular, the numerous ovules being borne upon projecting 
parietal placentae. The carpels are nearly always two in number, 
—only rarely and abnormally three. 
This type of unilocular ovary—the result of union of carpellary 
leaves at the margins only—will be readily distinguished from the 
type which occurs, e.g., in the Primulaceae and Lentibulariaceae, 
where the unilocular condition results, presumably, from the 
degradation of septa in the course of descent; this presumption is 
supported by the free-central character of the placentation. The 
former type, with parietal placentation, is to be regarded as 
relatively primitive, as urged in the last chapter; the latter is 
clearly secondary. The former type, again, is the rare exception 
among representatives of the stock with which we are concerned, 
and which we have dealt with so far; thus, in the Transitional 
1 See Lindley, The Vegetable Kingdom. 3rd edition, p. 686. 
