Note 88 — IDEAS FOR A PHYSIOGNOMY OF PLANTS.

p. 225—“Form of the Mimosæ.”

The delicate and feathery foliage of the Mimosæ, Acaciæ, Schrankiæ, and Desmanthus, may be regarded as peculiarly characteristic of tropical vegetation; although some representatives of this form may also be found without the tropics. In the Old Continent of the northern hemisphere, and indeed in Asia, I can instance only one low shrub, described by Marshal von Bieberstein as Acacia Stephaniana, but which, according to Kunth’s more recent investigations, is a species of the genus Prosopis. This social plant covers the arid plains of the province of Schirvan on the Kur (Cyrus), near New Schamach, as far as the ancient Araxes. Olivier found it also in the neighbourhood of Bagdad. It is the Acacia foliis bipinnatis mentioned by Buxbaum, and which extends towards the north as far as 42° lat.^[OK] In Africa the Acacia gummifera (Willd.), extends to Mogador, and therefore as far as 32° north lat.

In the New Continent, Acacia glandulosa (Michaux), and A. brachyloba (Willd.), adorn the banks of the Mississippi and Tennessee, and the Savannahs of the Illinois. The Schrankia uncinata was found by Michaux to penetrate from Florida northwards to Virginia (therefore as far as 37° north lat.). Gleditschia triacanthos is met with, according to Barton, to the east of the Alleghany mountains, as far as 38° north lat., and west of the same range even to 41° north lat. The extreme northern limit of Gleditschia monosperma is two degrees further southward. Such are the boundaries of the Mimosa form in the northern hemisphere, while in the southern hemisphere, beyond the tropic of Capricorn, simple-leaved Acaciæ are found as far as Van Dieman’s Land; the Acacia cavenia described by Claude Gay being even found in Chili between 30° and 37° south lat.^[OL] Chili has no true Mimosa, but three species of Acacia; and even in the north of Chili the Acacia cavenia grows only to a height of 12 or 13 feet, whilst in the south, as it approaches the sea-coast, it 308scarcely rises a foot above the ground. The most sensitive of the Mimosas which we saw in the northern portion of South America, are (next to the Mimosa pudica,) M. dormiens, M. somnians, and M. somniculosa. The irritability of the African sensitive plant was already noticed by Theophrastus (iv. 3), and by Pliny (xiii. 10); but I find the first description of the South American sensitive plants (Dormideras) in Herrera (Decad. ii. lib. iii. cap. 4). The plant first attracted the attention of the Spaniards, in 1518, in the Savannahs on the isthmus round Nombre de Dios (“parece como cosa sensible”), and it was pretended that the leaves (“de echura de una pluma de pajaros,”) only contracted together when they were touched with the finger, and not when brought in contact with a piece of wood. In the small swamps which surround the town of Mompox on the Magdalena River, we discovered a very beautiful aquatic Mimosa (Desmanthus lacustris), a representation of which is given in our “Plantes équinoxiales” (t. i. p. 55, pl. 16). In the chain of the Andes of Caxamarca we found two Alpine Mimosas (Mimosa montana and Acacia revoluta) growing at elevations of from 9000 to nearly 9600 feet above the level of the sea.

As yet no true Mimosa, (in the meaning of the word as established by Willdenow,) nor even any Inga, has been found in the temperate zone. Amongst all the Acacias the Oriental Acacia Julibrissin, which Forskäl has confounded with Mimosa arborea, endures the greatest degree of cold. In the Botanical Garden of Padua there is a high stem of considerable thickness growing in the open air, although the mean temperature of Padua is below 56° Fahrenheit.