460 
Saunders.—A Reversionary Character 
the paired valves, for as no knob is developed over the knife-edge suture 
these latter are not compressed into loop form (Figs. 20-9). 
4. The siliqua, though 2-valved, is somewhat curved, and has a pro¬ 
jecting rib of tissue running the whole length in the middle line of one 
commissure, and ending above in a free tongue-like process which juts out 
just below the knob proper to the commissure (Figs. 30-3). A cross- 
section shows the usual arrangement—a single median septum, two loculi, 
and four placentae, but the sutural arc on the one side is larger than the 
other, triangular in section, and shows three fibro-vascular cords, one 
belonging to the projecting rib and a small one on either side. The stig- 
matic configuration is peculiar. Over the larger commissure with its tongue¬ 
like process we find not a knob, but a second stylar canal surrounded by 
stigmatic papillae. 
5. The siliqua shows the interpolation of a small median valve (as 
much as, in one case, 3 mm.) above the level of the lateral valves (Figs. 34, 
35). There are three normal commissures from this level upwards, one in 
the median plane opposite the small valve, and one on either side of it 
(i. e. in the diagonal planes). Three septa formed from the three sutural 
arcs meet in the centre, forming a Y-shaped partition and rendering the 
ovary trilocular. 
These exceptional fruits were almost invariably among the lowest on 
the axis. 1 For working purposes it could in fact be assumed that if they 
were not seen among the first half-dozen they would not occur. 
5. Conchisions to be drawn from tJie above facts. 
These examples of Stock fruits of various constructional types shed 
fresh light upon the original ground plan of the Cruciferous gynoecium, 
and enable us to conceive how the existing type has been derived from it 
through processes of reduction and consolidation. The above facts all go 
to show that the gynoecium in its fullest present-day development in the 
Stock consists of eight carpels, four of which assume the form of valves and 
are arranged in two pairs, the median pair appearing to arise at a somewhat 
higher level than the lateral pair. 2 The other four alternate with the valves 
as though the latter constituted a single whorl, in precisely the same manner 
as the four petals alternate with the two pairs of sepals. These latter 
carpels are solid, compressed into the small space between the valves, and 
appear outwardly as broad or narrow commissures. They are almost 
invariably fertile, whereas the hollow (valve) carpels are probably only so in 
1 See also Peyvitsch, Pringsheim’s Jahrb., viii, 1872, p. 117. It is in flowers in this position 
that other exceptional constructions seem most frequently to occur, as e. g. ‘twinning ' (see Journ. of 
Genetics, vol. xi, 1921, p. 69), and the formation of extra stamens (7-S). 
2 It is not, however, always the case that the level of swelling out into valve shape indicates 
the true level of origin (see Cases 2 and 5 above). 
