Page:Encyclopædia Britannica, Ninth Edition, v. 14.djvu/572

 552 L I C L I C he got interpreters to translate for him (Sail, Jug., 17); and fortunately one record of an exploring voyage along the west coast, preserved in a temple in Carthage, was translated by some Greek traveller and is still available (see HANNO). For all that is known of the Carthaginian rule in Libya see CARTHAGE. Greek mariners must have visited Libya at a very early period, for the edible lotus of the northern coast is men tioned in the Odyssey. In the latter part of the 7th century B.C. the Greeks began to colonize the north coast. Between the Cartha ginian territory and the borders of Egypt they planted a number of cities, and the Pentapolis of which Gyrene was the chief was among the richest and most flourishing of all the Greek states (see GYRENE). When the Persians invaded Egypt they made some attempt to extend their empire over Libya; but the expedition of Cambyses (about 525 B.C.) was too unfortunate to encourage them to further efforts. The camel was introduced into Egypt under the Persian rule, and from this time it became easier to make long journeys over the Libyan deserts. Herodotus shows much knowledge of the Sahara, and it is clear that his account must be founded on the reports of traders and caravan guides well acquainted with the desert route. Under the Macedonian kings know ledge of Libya was much extended ; they sent exploring expeditions for scientific purposes into Abyssinia, while growing wealth and luxury caused a continually increas ing demand for the ivory, spices, and other produce of Libya. In the period 500-200 B.C. it seems certain that commerce was maintained with the countries beyond the Sahara in at least two ways by the Carthaginian ships trading along the Atlantic coast, and by the over land route across the desert to the Nile. The Roman conquest of Carthage closed the former route. Polybius indeed was commissioned by Scipio to explore the country, and sailed a long way down the west coast ; but the Romans themselves had not the maritime enterprise required for such voyages. The record which Polybius wrote for his friend Scipio is quoted by Pliny and Stephanus. Sallust also collected information about the country, and under the emperor Nero an exploring expedition was sent into Abyssinia. The Romans added more to the knowledge of Libya in other ways, by a better organization of the province and increased facilities of travel and trade, by the frontier wars against surrounding tribes, and finally by the expeditions sent directly into the heart of the country to procure wild animals for the amphitheatre. The passion of the Roman populace for seeing strange animals slaughtered in the public games was gratified by the emperors and magistrates. Enormous numbers of Libyan wild beasts were exhibited in the amphitheatre ; even hippopotami and alligators are mentioned. One Roman officer, Maternus, penetrated at least as far as Lake Chad. The Periplus of Arrian preserves a record of the trade along the east coast of Libya in the 1st century. In these ways a fairly accurate knowledge of northern Libya was obtained, and Ptolemy could, in the 2d century, construct a good map of Africa as far south as 11 N., though his idea of the shape of the continent further to the south is less accurate than that of Herodotus. See Ritter, Erdkunde, i. ; Heeren, Historical Researches, or in the German Idecn, vol. ii. ; and the geographical works of Forbigcr, Kiepert, Bunbury, &c. LIC AT A. See ALICATA, vol. i. p. 574. LICHENS (Lickenes) may briefly be defined as cellular perennial plants, furnished with a vegetative system containing gonidia, and with a reproductive system consisting of female thecasporous fruits and male spermo- gonous organs. They constitute a distinct class of cellular cryptogams, intermediate between algge and fungi, to both of which in some respects they present certain affinities. By the earlier authors they were regarded as being Aerophycse or terrestrial algae, while of recent years they have been viewed by some writers as being Ascomycetous fungi. From both of these, however, they are sufficiently distinguished and separated by the special structure of their thallus, by the presence of certain immediate principles proper to their tissues, and by their mode of life and nutrition. Their relations to these neighbouring classes, and their true systematic place, will be best elucidated on considering their structure and its bearings upon some recent speculations, Structure of Lichens. A complete lichen consists of a nutritive and vegetative system termed the thallus, and of reproductive bodies borne upon it in the form of apothecia and spermogones. Occasionally, however, there is no thallus present (e.g., Sphinctrina, various Lecideee, Endococcus), in which case the fructification is parasitical on the thalli of other lichens. I. Vegetative System. The thallus is very variable in external form and colour, as also in internal structure. 1. In external form it presents the following modifica tions. The fuliaceous thallus, which may be either peltate, i.e., rounded and entire, as in Umbilicaria, &c., or variously lobed and laciniated, as in Sticta, Parmelia, &c. This is the highest type of its development, and is some times very considerably expanded. (b) The fruticulose thallus, which sometimes is filamentose, as in Epliebe, and may be either erect, becoming pendulous, as in Usnea, Hamalina, &c., or prostrate, as in Alectoria jubata, var. chalybeiformis. It is usually divided into branches and branchlets, bearing some resemblance to a miniature shrub amongst the Phanerogamia. An erect cylindrical thallus terminated by the fruit is termed a podetium, as in Cladonia. (c) The crustaceans thallus, which is the most common of all, forms a mere crust on the substratum, varying in thickness, and may be squamose (in Squamaria], radiate (in Placodium), areolate, granulose, or pulverulent (in various Lecanorx and Lecidex). In its pulverulent state it is either the rudimentary or the abortive condition of many species, (d) The hypophloeodal thallus is often concealed beneath the bark of trees (as in some Verrucarix and Arthonise), or enters into the fibres of wood (as in Xylographa and Agyrium), being indicated externally only by a very thin film or macula. To this may also be referred the evanescent thallus which is denoted solely by gonidia sparingly scattered on the stone or wood (as in some Caliciei and Lecidese). This is the simplest form under which lichenose vegetation occurs. These two latter forms of thalli may be either determinate, i.e., of a definite shape with a distinct margin or boundary, or effuse, i.e., spreading extensively over the substratum with no visible limits. The differences in these forms are no doubt connected with differences in the chemical composition of the thallus. In colour also the thallus externally is very variable. In the dry and more typical state it is most frequently white or whitish, and almost as often greyish or greyish glaucous. Less com monly it is of different shades of brown, red, yellow, and black. These various colours do not originate from any colouring matters contained in the cells themselves, but, according to investigations made by Nylander (see Flora, 1879, p. 558) they depend upon such as are deposited in the granulations and cellular walls, whence they appear on the epithallus. In the moist state of the thallus these colours are much less apparent, as the textures then become more or less translucent, and the epithallus usually presents the greenish colour of the gonidia (e.g., Parmelia Borreri, Peltidea apkthosa, Umbilicaria pustulata, and pulverulent Lecidex).