CRUCIFERAE 
343 
petals and 4 inner sta. are supposed to be due to branching. Others 
again regard it as 4-merous (see e.g. Klein in Bot . Centr. 58, p. 197). 
A full discussion of the point may be found in Eichler’s Bluthendiagr. 
or in Asa Gray’s Struct. Bot . p. 206. 
On the bases of the sta. are the nectaries, the honey being secreted 
into the often gibbous bases of the inner sepals. The sepals often 
stand almost straight up, and the petals are then provided with claws 
and spread out horizontally beyond the sepals. The honey is thus 
concealed to some extent and protected from rain. The majority of 
the order exhibit this construction more or less, thus coming into the 
biological group of flowers AB (see p. 90). In many genera the firs, 
are arranged in corymbs, thus getting the advantage of many firs, 
being massed together on one level (cf. Umbelliferae and Compositae). 
Insects visiting the firs, touch the anthers with one side of their bodies 
and the stigma with the other, and may in this way effect cross-fertili- 
sation, as they go sometimes to one, sometimes to the other, side of the 
fir. Dichogamy is frequent, but not well marked, and in almost all 
cases self-fertilisation ultimately occurs. [For details see Muller, Fert. 
of Firs.] 
The fruit is a capsule of pod-like form ; if it be at least three times 
as long as it is broad it is called a siliqua , if shorter it is called a 
silicula. It is divided into two by the replum and is usually thin and 
membranous. Dehiscence occurs by the valves breaking away from 
below upwards, leaving the replum with the seeds pressed against it 
and adhering. The fruit may be flattened in two ways, either parallel 
to or at right angles to the replum; this character is of systematic 
importance. It may also be jointed between the seeds as in a lomen- 
tum (Leguminosae). Achene-like one seeded fruits occur in a few 
genera. Others have subterranean fruits (Cardamine sp. &c.). 
The characters of the seed are also of great importance in the 
classification of the order. The seed is exalbuminous : the testa is 
very often mucilaginous, swelling up when wetted (e.g. the familiar 
case of mustard seed) ; this property is valuable for fixing the seed in 
a favourable spot for germination. The ovules being campylotropous, 
the embryo sacs, and thus the embryos, are curved, usually with 
the radicle in one half of the seed, the cotyledons in the other. The 
shape of the embryo and the position of the radicle with regard to 
the cotyledons are of much importance. The chief cases are : 
(r) radicle incumbent (or embryo notorhizal ) i.e. lying on the 
back of one cotyledon, the cotyledons not being folded on them- 
selves; this may be shown thus o||, the o representing the radicle; 
(2) accumbent (or embryo pleurorhizal ), o = , the radicle against the 
edges of the cotyledons; (3) orthoplocous (cotyledons conduplicate)> 
o>>; (4) spirolobous , as in (1) but cotyledons once folded, o||||; 
(5) diplecolobous , ditto twice or more folded, o||||||||. 
For plants of economic value see especially Brassica, Nasturtium, 
