CHAPTER XII.

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.