in the Stock (Matthiola incana ). 457 
sideration of the facts set forth below will show the grounds upon which' 
this statement is based. 
Variously curved and coiled fruits had been noticed in the Stock in 
successive seasons, but their appearance was so suggestive of the kind of 
unilateral injury so often caused by insects and other agencies that no close 
examination of them was made until their abundance in the exceptional 
season of 1921 attracted attention afresh. It was then seen that their 
asymmetric shape was not due to accidental lesion but to an unusual 
anatomical construction. It was furthermore found that this structural 
variation was sometimes, though more rarely, symmetrical, the siliqua then 
remaining straight. A description of some of these cases will serve to make 
clear the nature of these anatomical peculiarities. 
4. Exceptional forms of siliqua in the Stock. 
1. The siliqua is 4-valved, with four sometimes rounded but more often 1 
flat or concave sides and a small arc at each angle, trilocular, with two 
complete partitions in planes parallel to each other and to the median plane. 
The valve edges are not incurved and are not utilized in the formation of the 
septa, which are developed entirely from the small arcs. 1 Ovules arise on 
either side and at each end of each septum, but probably not more than 
three or four of these eight placentae ever mature seed. There are four 
stigmatic surfaces separated by four knobs, one at each corner, the stigma 
of each valve forming a loop, or those of the median pair remaining straight. 
If, as may happen, one side of the siliqua is rather more strongly developed 
than the other the septum joining the commissural arcs on the weaker side 
may not be formed. If the development is very unequal the fruit becomes 
spirally coiled (Figs. 12-18). 
2. The siliqua is bluntly 4-angled, with the anterior and posterior 
surfaces often flat or concave. In the lower region there are two commis¬ 
sures of normal appearance, i. e. each is defined by two contour lines. 
About one-quarter up the length of the siliqua one commissure broadens 
out, and a small valve is interpolated which is continued up to the top. 
A cross-section through the lower region shows one normal convex lateral 
valve in contact on either side with a small arc (commissure). The one arc 
has the usual vascular supply ; in the other tzvo vascular cords are present. 
It is in this latter suture that the small new valve is developed higher up, 
between the two fibro-vascular strands which have now diverged. The 
1 In this connexion it is interesting to note that just a century ago, on grounds which he formu¬ 
lates, Lestiboudois expressed himself on this point thus : ‘ I do not believe that the edges of the 
valves turn in to form the septum’ (Memoire sur les Fruits siliqueux). His belief was well founded. 
In regard to this point the schematic diagrams for the Rhoeadales in which such incurving is in¬ 
variably represented are misleading. They represent not a reality but an abstract conception which 
is in fact erroneous. 
