or “crozier’s staff,” and then, at the beginning of the 16th century, by “crozier” (see J. T. Taylor, Archaeologia, Iii., “On the Use of the Terms Crosier, Pastoral Staff and Cross”).
CRUCIAL (from Lat. crux, a cross), that which has the form of
a cross, as the “crucial ligaments” of the knee-joint, which
cross each other, connecting the femur and the tibia. From
Francis Bacon’s expression instantia crucis (taken, as he says,
from the finger-post or crux at cross-roads) for a phenomenon
which decides between two causes which have each similar
analogies in its favour, comes the use of “crucial” for that which
decides between two alternatives, hence, generally, as a synonym
for “critical.” The word is also used, with a reference to the use
of a “crucible,” of something which tests and tries.
CRUCIFERAE, or Crucifer family, a natural order of flowering
plants, which derives its name from the cruciform arrangement
of the four petals of the flower. It is an order of herbaceous
plants, many of which, such as wallflower, stock, mustard,
cabbage, radish and others, are well-known garden or field-plants.
Many of the plants are annuals; among these are some of the
commonest weeds of cultivation, shepherd’s purse (Capsella
Bursa-pastoris), charlock (Brassica Sinapis), and such common
plants as hedge mustard (Sisymbrium officinale), Jack-by-the-hedge
(S. Alliaria or Alliaria officinalis). Others are biennials
producing a number of leaves on a very short stem in the first
year, and in the second sending up a flowering shoot at the
expense of the nourishment stored in the thick tap-root during
the previous season. Under cultivation this root becomes much
enlarged, as in turnip, swede and others. Wallflower (Cheiranthus Cheiri) (fig. 1) is a perennial. The leaves when borne on an
elongated stem are arranged alternately and have no stipules.
The flowers are arranged in racemes without bracts; during the
life of the flower its stalk continues to grow so that the open
flowers of an inflorescence stand on a level (that is, are
corymbose). The flowers are regular, with four free sepals
arranged in two pairs at right angles, four petals arranged crosswise
in one series, and two sets of stamens, an outer with two
members and an inner with four, in two pairs placed in the
middle line of the flower and at right angles to the outer series.
The four inner stamens are longer than the two outer; and the
stamens are hence collectively described as tetradynamous.
The pistil, which is above the rest of the members of the flower,
consists of two carpels joined at their edges to form the ovary,
which becomes two-celled by subsequent ingrowth of a septum
from these united edges; a row of ovules springs from each
edge. The fruit is a pod or siliqua splitting by two valves from
below upwards and leaving the placentas with the seeds attached
to the replum or framework of the septum. The seeds are filled
with the large embryo, the two cotyledons of which are variously
folded. In germination the cotyledons come above ground and
form the first green leaves of the plant.
 |
| Fig. 1.—Wallflower (Cheiranthus Cheiri), reduced. 1, Flower in vertical section. 2, Horizontal plan of arrangement of flower in Barbarea. |
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| Fig. 2.—Cruciferae. Floral Diagram (Brassica). |
Fig. 3.—Cardamine pratensis. Flower with Perianth removed. (After Baillon.) |
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| Fig. 4.—Cruciferous Fruits. (After Baillon.) | |
|
A, Cheiranthus Cheiri. B, Lepidium sativum. C, Capsella Bursa-pastoris. |
D, Lunaria biennis, showing the septum after the carpels have fallen away. E, Crambe maritima. |
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| Fig. 5.—Seeds of Cruciferae cut across to show the radicle and cotyledons. (After Baillon.) |
| A, Cheiranthus Cheiri. |
| B, Sisymbrium Alliaria. |
| Figures 2-5 are from Strasburger’s Lehrbuch der Botanik, by permission of Gustav Fischer. |
Pollination is effected by aid of insects. The petals are generally white or yellow, more rarely lilac or some other colour, and between the bases of the stamens are honey-glands. Some or all of the anthers become twisted so that insects in probing for honey will touch the anthers with one side of their head and the capitate stigma with the other. Owing, however, to the close proximity of stigma and anthers, very slight irregularity in the movements of the visiting insect will cause self-pollination, which may also occur by the dropping of pollen from the anthers of the larger stamens on to the stigma.
Cruciferae is a large order containing nearly 200 genera and about 1200 species. It has a world-wide distribution, but finds its chief development in the temperate and frigid zones, especially of the northern hemisphere, and as Alpine plants. In the subdivision of the order into tribes use is made of differences in the form of the fruit and the manner of folding of the embryo. When the fruit is several times longer than broad it is known as a siliqua, as in stock or wallflower; when about as long as broad, a silicula, as in shepherd’s purse.
