THE GENUS LEUCHTENBERGIA.
(Named in honour of Prince Leuchtenberg.)
Among the many instances of plant mimicry that occur in the Cactus
order, the most remarkable is the plant here figured. Remove the flower
from Leuchtenbergia, and very few people indeed would think of calling
it a Cactus, but would probably consider it a short-leaved Yucca. In
habit, in form, in leaf, and in texture, it more resembles a Yucca or an
Agave than anything else, and when first introduced it was considered
such by the Kew authorities until it flowered. The leaves, or rather
tubercles, are sometimes longer and slenderer than in Fig. 74. The
nearest approach to this plant is Mamillaria longimamma, in which the
tubercles are 1 in. or more long, finger-shaped, and crowned with a few
hair-like spines. But the Leuchtenbergia bears its flowers on the ends
of the tubercles, and not from the axils, as in all others. This
peculiarity leads one to infer that tubercles are modified branches, the
spines representing the leaves. Some species of Mamillaria and
Echinocactus develop young plants from the tops of their tubercles; and
this also points to the probability that the latter are branches. In
Leuchtenbergia, the tubercles fall away as the plant increases in
height, leaving a bare, woody stem similar to that of a Yucca.
Cultivation.--The Leuchtenbergia has always been difficult to keep in
health. It thrives best when kept in a warm, sunny house during winter,
and in an exposed, airy, warm position under a frame during summer. It
may be watered regularly whilst growing--that is, from April to
September--and kept quite dry all winter. The soil should be
well-drained loam, and the roots should have plenty of room. A specimen
may be seen in the Kew collection.
Propagation.--This may be effected from seeds, or by removing the head
from an old plant, putting the former in sand, and placing it under a
bell-glass to root, watering it only about once a week till roots are
formed. The old stem should be kept dry for about two months, and then
watered and placed in a sunny, moist position, where it can be syringed
once a day. A shelf in a stove is the best position for it. Here it will
form young buds in the axils of the withered tubercles, and on the edges
of the persistent parts of the tubercles themselves. They first appear
in the form of tiny tufts of yellowish down, and gradually develop till
the first leaf-like tubercle appears. When large enough, the buds may be
removed and planted in small pots to root. If an old plant is dealt with
in this way in April, a batch of young ones should be developed and
rooted by October. Grafting does not appear to have ever been tried for
this plant. When sick, the plant should be carefully washed, and all
decayed parts cut away; it may then be planted in very sandy loam, and
kept under a bell-glass till rooted.
[Illustration: FIG. 74. LEUCHTENBERGIA PRINCIPIS.]
SPECIES.
L. principis (noble); Fig. 74.--This, the only species known, was
introduced from Mexico to Kew in 1847, and flowered the following year.
The plant attains a height of 1 ft. or more, the stem being erect, stout,
clothed with the persistent, scale-like bases of the old, fallen-away
tubercles, the bases having dried up and tightened round the stem. The
upper part is clothed with the curved, leaf-like tubercles, from 3 in. to
6 in. long, grey-green in colour, succulent, with a tough skin,
triangular, and gradually narrowed to a blunt point, upon which are half
a dozen or more thin, flexuous, horny filaments, neither spines nor
hairs in appearance, but almost hay-like; the central one is about 5 in.
long, and the others about half that length. The flowers are borne on
the ends of the young, partly-developed tubercles, near the centre of
the head; they are erect, tubular, 3 in. to 4 in. long, scaly, gradually
widening upwards; the sepals and petals are numerous, and form a
beautiful flower of the ordinary Cactus type, quite 4 in. across, and of
a rich, clear yellow colour. The anthers, which also are yellow, form a
column in the centre, through which the nine-rayed stigma protrudes.
Strong plants sometimes produce two flowers together.