Note 26 — PHYSIOGNOMY OF PLANTS.

p. 27.—“The form of Aloës.”

To this group of plants, characterised by so great a similarity of physiognomy, belong; Yucca aloifolia, which extends as far north as Florida and South Carolina; Y. angustifolia (Nutt.) which advances as far as the banks of the Missouri; Aletris arborea; the Dragon-tree of the Canaries and two other Dræcænas from New Zealand; arborescent Euphorbias; Aloë dichotoma (Linn.) (formerly the genus Rhipidodendrum of Willdenow); and the celebrated Koker-boom of Southern Africa with a trunk twenty-one feet high and above four feet thick, and a top of 400 (426 Engl.) feet in circumference. (Patterson, Reisen in das Land der Hottentotten und der Kaffern, 1790, S. 55.) The forms which I have thus brought together belong to very different families: to the Liliaceæ, Asphodeleæ, Pandaneæ, Amaryllideæ, and Euphorbiaceæ; all, however, with the exception of the last, belonging to the great division of the Monocotyledones. A Pandanea, Phytelephas macrocarpa (Ruiz,) which we found in New Granada on the banks of the Magdalena, with its pinnated leaves, quite resembles in appearance a small palm-tree. This Phytelephas, of which the Indian name is Tagua, is besides, as Kunth remarks, the only one of the Pandaneæ found (according to our present knowledge) in the New Continent. The singular Agave-like and at the same time very tall-stemmed Doryanthes excelsa of New South Wales, which was first described by the acutely observing Correa de Serra, is an Amaryllidea, like our low-growing Narcissuses and Jonquils.

In the Candelabra shape of plants of the Aloë form, we must not confound the branches of an arborescent stem with flower-stalks. It is the latter which in the American Aloë (Agave Americana, Maguey de Cocuyza, which is entirely wanting in Chili) as well as in the Yucca acaulis, (Maguey de Cocuy) presents in the rapid and gigantic development of the inflorescence a candelabrum-like arrangement of the flowers which, as is well known, is but too transient a phenomenon. In some arborescent Euphorbias, on the other hand, the physiognomic effect is given by the branches and their division, or by ramification properly so called. Lichtenstein, in his “Reisen im südlichen Africa” (Th. i. S. 370), gives a vivid description of the impression made upon him by the appearance of a Euphorbia officinarum which he found in the “Chamtoos Rivier,” in the Colony of the Cape of Good Hope; the form of the tree was so symmetrical that the candelabrum-like arrangement was regularly repeated on a smaller scale in each of the subdivisions of the larger branches up to 32 English feet high. All the branches were armed with sharp spines.

Palms, Yuccas, Aloes, tall-stemmed Ferns, some Aralias, and the Theophrasta where I have seen it growing luxuriantly, different as they are in the structure of their flowers, yet offer to the eye in the nakedness (absence of branches) of their stems, and in the ornamental character of their tops or crowns, a certain degree of physiognomic resemblance.

The Melanoselinum decipiens (Hofm.), which is sometimes upwards of 10 or 12 feet high, and which has been introduced into our gardens from Madeira, belongs to a peculiar group of arborescent umbelliferous plants to which Araliaceæ are otherwise allied, and with which other plants which will doubtless be discovered in course of time will be associated. Ferula, Heracleum, and Thapsia, do indeed attain a considerable height, but they are still herbaceous plants. Melanoselinum is still almost entirely alone as an umbelliferous tree; Bupleurum (Tenonia) fruticosum (Linn.) of the shores of the Mediterranean; Bubon galbanum of the Cape, and Crithmum maritimum of our sea-shores, are only shrubs. On the other hand, the tropical zone, in which, according to the old and very just remark of Adanson, Umbelliferæ and Cruciferæ are almost entirely wanting in the plains, presented to us on the high ridges of the American Andes the smallest and most dwarf-like of all umbelliferous plants. Among 38 species of plants which we collected at elevations where the mean temperature is below 10° Reaumur (54°.5 Fah.), there vegetate almost like mosses, and as if they made part of the rock and of the often frozen earth, at an elevation of 12600 (13430 English) feet above the level of the sea, Myrrhis andicola, Fragosa arctioïdes, and Pectophytum pedunculare, intermingled with which there is an equally dwarfed Alpine Draba. The only umbelliferous plants growing in the low grounds within the tropics observed by us in the New Continent were two species of Hydrocotyle (H. umbellata and H. leptostachya) between Havannah and Batabano; therefore at the extreme limits of the torrid Zone.