Page:The New International Encyclopædia 1st ed. v. 09.djvu/849

* HEPATIC^. 783 HEPATICiE. called a 'thallus' (q.v. ). By virtue of thia po- sition the body is 'dorsiventral,' since the two surfaces are unlike. The upper (dorsal) sur- face, exposed to the light, develops structures ac- cordingly; while the under (ventral) surface IMBEDDED ANTHEKIDIUM OP ANTHOCEE08. is against the substratum and develops root-like processes as hold-fasts and absorbing organs. There are three well-defined groups of liver- -^^^ surface, but develops reproductive structures from its upper surface. In many cases there is a budding form of reproduction; little cups (cupulcs) appear often in great numbers in which small disk-like bodies (gemnuc) are formed. When these gemnue are scattered they again produce new plants. Upon the upper sur- face also the sex organs are carried, and in Jlar- chantia itself they are borne upon the summit of a conspicuous erect branch. As a rule the two sex organs (antheridia and archegonia) are borne upon dill'ercnt plants. The jungcrniunnialcs include many more spe- cies than either of the others. These forms often ARCHEGONIUSI OF PORELLA. "With three sperms approaching the neck. ^vorts, each of which represents a special line of development. In the Marchantiales, the thallus body remains simple in form, like a flat green SECTION OP THALLUS OP ANTH0CEB08. Showing antheridia in pits. disk, but becomes thick and rather complex in -structure. This thickish body not only produces root-like processes (rhizoids) from its under GERMINATION OP SPORES OPCONOCEPHALCS. grow in very dry situations, as on rocks, tree- trunks, etc., and are often mistaken for delicate mosses. Their resemblance to mosses suggests one of the chief features. The prostrate thallus body remains simple in structure, but becomes very much modified in form, being organized into a central stem-like axis which bears two rows of small foliage leaves. As a consequence the Jungermanniales are usually spoken of as the 'leafy liverworts.' The Anthocerotales comprise comparatively few forms, but these are of great interest since they are supposed to represent forms which have given rise to the mosses and perhaps to the ferns rBO88-8E0TION OP SPOROQONirTM OP ANTHOCEBOS. Showing sporeH within, uiul Hurrouuded by heavy green tissue. also. The fliallus body is very simple, both in structure and in form, but the chief interest is in connection with the spore-case, which is elon-