30 EXODUS EXOGENS route of the exodus is now fairly established. The Hebrews marched S. E. for three days, then turned S. W., and finally E., their fourth encampment being at Pi-hahiroth, a few miles S. of the present Suez, near a point where the gulf of Suez suddenly narrows to a quarter of its former width. They were on a narrow tri- angular plain bounded N. by a range of cliffs and S. E. by the expansion of the sea. The Egyptian king had meanwhile gathered a con- siderable force, especially of chariots, the cav- alry of the time, and was following hard upon the fugitives, who, hemmed in between the cliffs and the water, had no apparent way of escape. At the point here assumed as that of the passage there is still a shallow, stretching from shore to shore, almost fordable at low tide. " The Lord caused the sea to go by a strong east wind all that night, and made the sea dry land, and the waters were divided." That is, the east (or more strictly easterly) wind piled up the waters toward the head of the gulf, leaving the shallow dry. The idea which painters have popularized, that the waters stood up as a solid wall on each side, is wholly without warrant in the sacred text ; all that is implied is that there was deep water on each side of the passage. The crossing was apparently made during the day. At night- fall the Egyptians came up, and seeing the pas- sage still dry attempted to follow. It is ap- parently implied in the text, though not directly stated, that the wind now shifted; for an east- erly wind would have carried the bodies of the Egyptians to the west side, whereas the Hebrews beheld them thrown on the eastern shore, upon which they were. All the impli- cations of the narrative are that the reflux of the waters was gradual ; for we are told that "the Lord took off [or rather clogged up] their chariot wheels, and made them go heavily;" that is, probably, the returning waters slowly filtered into the sand, making it difficult for the chariots to move. The Egyptians, seeing the waters rising, endeavored to retreat; but in the darkness, their returning van encounter- ing their advancing rear, they could go neither way, and were swallowed up by the rising tide. That this passage was really miraculous is everywhere asserted or implied by all the sacred writers who speak of it. Their route at first lay parallel with the eastern shore of the gulf of Suez, which they apparently touched at one point, the halting places being specified, and several of them are identified with reasonable certainty. At one of these, Rephidim, they were attacked by a body of Amalekites, who were defeated by the Israel- ites under the command of Joshua. After three months they reached the region of Sinai, in the heart of the Arabian peninsula, where they remained until 14 months after their de- parture from Egypt, and then set off upon their long wanderings toward the promised land. During this interval the law was given, and those religious and civil institutions were framed which in the course of a generation transformed the Hebrews into a military peo- ple, able to cope with the enemies whom they were about to encounter. The history, as re- lated in the book of Exodus, properly closes with the encampment around Sinai, and is con- tinued in the book of Numbers. (See SINAI.) The best works on the historical narrative are Ebers's Aegypten und die BiicJier Hose's (Leip- sic, 1868 et seq.} and DurcJi Oosen zum Sinai (Leipsic, 1872), and Palmer's " The Desert of the Exodus " (London, 1872). EXOGENS (Gr. efw, outward, and -yevvav, to generate), a class of plants so called because their woody matter is increased by additions to the outside of that which first surrounds the . central pith. As there are no specific limits to the age of exogenous trees, their diameter indefinitely increases by this annual process, a distinct external layer being added by each year's growth. The stem of an exogen con- sists of a central column of pith or medulla, woody zones, and bark. Processes from the central medulla called medullary rays cross the zones transversely. The bark of an exogen parts readily from the underlying wood at a particular season of the year, when a viscid secretion called cambium is produced between the wood and the inner surface of the bark. It is at this period that the leaves expand and the trunk lengthens. The woody fibres in the leaves are prolonged into the stem or trunk, passing down among the cambium, and adher- ing partly to the wood and partly to the bark of the previous year. By this means new living matter is continually deposited upon the outer portion of the woody stem and the inner portions of the bark. It is in this part of the stem that the intensest vitality exists, the outer and older layers of the bark and the inner and older concentric rings of the wood becoming inert and falling off or decaying without in- jury to the vegetative parts. The office of the medullary processes is very important as means of communication between the centre of the stem and the outside layers or rings ; and they are conduits, so to speak, by which the fluid matter passing down the bark can reach the wood next the medulla or pith. These pro- cesses, which resemble thin plates, are of a spongy nature similar to that of the pith from which they originated. They sometimes as- sume sinuosities and undergo partial oblitera- tion; and sometimes the wood itself assumes an excessive irregularity. As these circum- stances are to be found mostly in tropical ex- ogenous trees, vines, and climbers, difficulty is sometimes experienced in perceiving from transverse sections their claims to be consid- ered as exogens. This natural character of an outward growth in the exogens is asso- ciated with other peculiarities of development of other organs. Thus, the leaves have veins ramifying from the midrib outwardly to the circumference; or if there are several ribs, the veins are still of the same quality, so as to
