Page:The New International Encyclopædia 1st ed. v. 01.djvu/866

ARCHEGONIUM. fers, etc., which together are often spoken of as Arehegoniutes. It is a Hask-shaped organ, consisting of a neck more or less elongated and a venter more or less bulbous. A single egg occupies the venter, and in the process of fer- tilization the sperm enters by the open neck of the arehegonium and comes in contact with the egg. Among the mosses the arehegonium is a free and often stalked organ. Aniong the liver- worts the arehegonia are variously disposed on the thallus-body, while in mosses they are borne in a cluster at the apex of the leafy shoot or of its branches, the terminal rosette of more or less modified leaves forming what is often called a 'moss flower.' Among the ferns the arehegonia are usually borne upon the under side of the in- conspicuous sexual plant (prothallium), the ven- ters being imbedded in the tissue and the necks more or less projecting. In the water ferns, quillworts, and little club-mosses, the female plant is developed as a tissue within the spore, whose heavy wall breaks or ci-acks at a certain place, and in the exposed part of the female plant the arehegonia are developed. Among the conifers the spore, %ith its contained female plant, is retained within the ovule, and hence the arehegonia are not exposed, but lie im- bedded in the superficial part of the female plant (endosperm), toward the micropyle (the pas- sageway left by the integument). Among the conifers the male cells are brought to the arehe- gonium by growing pollen-tubes. The pollen- grain, containing the male cells, rests at the base of the micropyle, upon the apex of the nueellus (central part of the ovule). The tube penetrates the tissue of the nueellus and reaches the embrvo-sac (megaspore), just within which are the arehegonium necks. It then pierces the sac-wall, enters and crushes the neck, and dis- charges its male cells into the egg.

Among the flowering plants no arehegonia are developed, the embr3'o-sac containing a free egg, along with other free cells of a much-reduced female plant.

ARCHEOONIA. (a) of a moss. (/>) of a forn. and (c) of a liverwort, show- ing in each case the neck and the venter eontainiii^rtiie e^r*r. The development of an arehegonium and its preparation for fertilization are matters of great morphological interest. It begins as a single superficial cell of the sexual plant. By repeated cell divisions the layer of cells constituting the neck and venter is formed, and this surrounds a single row of axial cells. The cells of this row (variable in number) which lie within the neck are called the "neck canal cells." while the lowest cell of the row, the one within the venter, forms the egg. When the areliegonium. is nearly mature the row of neck canal cells breaks down and leaves an open neck: and usually just before fertilization the cell in the venter cuts off a small cell toward the neck called the "ventral canal cell," which rapidly disorganizes and leaves the egg free and alone in the venter, ready for the approach of the sperms through the neck. One of the interesting facts in connection with arehegonia is that the apical neck cells secrete a substance which attracts the sperms toward them. For example, this substance is not the same in mosses and ferns, so that even if arehe- gonia of the two groups are close together the moss sperms and the fern sperms will be at- tracted only to their own arehegonia. ARCHEGOSAURUS, iir'ks-go-sa'rus. Se« Stegocephalia. ARCHELAUS, iir'ka-la'us (Gk. 'ApxAaos, Archel'Kj.i). — (ll One of the Heraclid* who, when driven by his brothers from his native land, fled to ^Macedonia and founded the town of -Egfe. He was the mythical founder of the royal house of ilacedonia. — (2) A Greek philoso- pher and pupil of Anaxagoras. He was born at Athens, and was the son of ApoUodorus or Jlyson. The outlines of his system were those of his teacher, but for the details of his cosmol- ogy he went back to the ideas of the earlier Ionic physicists. He admitted a primitive matter, con- sisting of infinite particles similar in nature to the bodies formed from them. He also admitted a ruling ilind. flatter and mind he held to be mingled, and identified the primitive matter with air. Out of this air, tlius endowed with mind, there arose, by processes of thickening and thin- ning.cold and heat, or water and fire — the former passive, the latter active. From the action of fire and water were formed the atmosphere and the mud out of which the heavenly bodies were developed. Living organized beings, at first of low type, sprang from the mud, and gradually the races of animals were formed. JIan he held to be superior In other beings, by reason of his artistic and moral powers. — ( 3 ) King of. Mace- donia, natural son of Perdiccas II. He came to the throne in B.C. 413. after murdering the rightful heir. Archelaus improved the internal condition of his kingdom, introduced clumges in the currency, improved the army, and showed himself a warm patron of a'rt and literature. Euripides, Zeuxis, and other men of eminence visited his court, and only Socrates refused an invitation to go thither. The palace of Archelaus was adorned with magnificent paintings by Zeuxis. Archelaus was either murdered or acci- dentally slain by his favorite, Craticus or Cra- teras, i'n B.C. 30!). — (4) A distinguislied general of ilithridates. In the winter of B.C. 88-S7 he was sent to Greece with a large fleet and army to oppose the Romans in that quarter. On the