. Foundations of Botany. Botany. 278 FOUNDATIONS OF BOTANY on the carbon dioxide gas which the plant absorbs, that is, arranged abont rather large air chambers. Reproduction is of two kinds, sexual and asexual, and the organs by which it is carried on are complicated and highly organized. An alternation of generations occurs, that is, the life history of any species embraces two forms: a sexual generation, which produces two kinds of cells that by their union give rise to a new plant; the asexual genera- tion, which multiplies freely by means of special cells known as spores. THE STUDY OF MARC
. Foundations of Botany. Botany. 278 FOUNDATIONS OF BOTANY on the carbon dioxide gas which the plant absorbs, that is, arranged abont rather large air chambers. Reproduction is of two kinds, sexual and asexual, and the organs by which it is carried on are complicated and highly organized. An alternation of generations occurs, that is, the life history of any species embraces two forms: a sexual generation, which produces two kinds of cells that by their union give rise to a new plant; the asexual genera- tion, which multiplies freely by means of special cells known as spores. THE STUDY OF MARCHANTIA. Fig. 202. —Part of Female Thallus of M. disjuncta. (Enlarged.) fr, female receptacle ; c, cups with gemmae. 335. Occurrence.— Marchantia grows on soil or rocks in damp shaded places and is widely distributed. 336. The Thallus. —In general form the thallus bears some resem- blance to that of some of the lichens, as Parmelia, but is plainly different in color, mode of branching, and internal structure under the microscope. Under the microscope (see below) the individual cells may be compared with those of the medullary layer in Physcia. Note the color and general shape of the thallus and study care- fully the mode of branching. The origin of the growing cells is at the tip, but cells so originating afterward multiply more rapidly, so that the tip comes to be in a notch. Viewing the thallus as an opaque object, note the diamond-shaped network on the upper surface and the dot-like circle in the middle of each diamond. Examine the under surface for (1) rhizoids and (2) Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Bergen, Joseph Y. (Joseph Young), 1851-1917. Boston, Ginn & company
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