. A textbook of botany for colleges and universities ... Botany. THALLOPHYTES II reproduction only by vegetative multiplication, the cell-divisions being simple but in remarkably rapid succession. However, in most forms there is no chlorophyll, so that bacteria in the main are parasites and saprophytes. The immense economic importance of bacteria has stimulated their investigation to such an extent that bacteriology has become a distinct field of research, with its special technique. An outline of plant mor- phology can only indicate the existence of this great region of research, for to enter
. A textbook of botany for colleges and universities ... Botany. THALLOPHYTES II reproduction only by vegetative multiplication, the cell-divisions being simple but in remarkably rapid succession. However, in most forms there is no chlorophyll, so that bacteria in the main are parasites and saprophytes. The immense economic importance of bacteria has stimulated their investigation to such an extent that bacteriology has become a distinct field of research, with its special technique. An outline of plant mor- phology can only indicate the existence of this great region of research, for to enter it would demand a course in bacteriology; but bacteria are plants, and their general place among other plants must be considered. Bacteria include the smallest known organisms, cells having been measured that are only ™rn- ^n diameter. The cells are either solitary or they may form filaments, as among the Cyanophyceae. For general purposes, individual cells are often referred to three form groups : coccus forms, in which the cells are spherical; bacterium or bacillus forms, in which the cells are oblong or have the form of short rods; and spirillum forms, in which the cells are curved (figs. 13-20). When these various forms of cells enter into the structure of fila- ments, corresponding varia- tions in the form of the filaments follow. The occurrence of bacteria may be described as almost literally every- where: in waters of every depth, in air, in soil, in all organic bodies, living or dead, etc. Their resistance to conditions impossible for other plants to endure is remarkable—a feature suggested by their asso- ciates, the Cyanophyceae. Extreme cold, high temperatures, and desic- cation that would destroy ordinary plants are successfully withstood by bacteria. Structure. —The structure of the bacterial cell appears to be extremely simple; in fact it may be said to be almost structureless. The proto-. FlGS. 13-20. — Bacteria: 13, coccus form, from pus; 14-18, b
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