Protococcus (prō′tō̇-kŏk′kŭs), a genus of plants which are among the simplest of the green algæ. The mature plants are single, spherical, green cells, which occur in masses. See Chlorophyceæ.
Protogyny (prō̇-tŏj′ĭ′nĭ) (in plants), a condition in which the stigma is ready to receive before the pollen of the same flower is ready for shedding. See Pollination.
Protonema (prō′tō̇-nē′ma) (in plants). When the asexual spores of mosses germinate, they at first produce green, branching filaments, which are prostrate and resemble ordinary green algæ. Upon this filamentous body the ordinary leafy branches arise. This algæ-like body is known as the protonema. See Musci.
Protoplasm (prō′tō̇-plaz’m), the living substance in animals and plants. Huxley called it the “physical basis of life.” It is the only substance endowed with life. It is very similar in animals and plants, and within it all living activities take place. It is a jelly-like, colorless substance, appearing finely granular under the microscope. It is composed of two parts: one more solid, which stains deeply with dyes (chromatin), and a fluid part (achromatin), which stains very faintly or not at all. The discovery of protoplasm and the gradual appreciation of the part it plays in the living world were among the greatest scientific advancements of the nineteenth century. In 1835 Dujardin, a French naturalist, was studying the simplest animals (Protozoa) under the microscope. He observed that their bodies were composed of a sort of transparent jelly, that moved and contracted and showed evidences of being alive. This soft, jelly-like substance he called Sarcode, and described it as living matter endowed with life. In 1846 Hugo von Mohl, a botanist, called attention to the viscid contents of plant-cells, for which he proposed the name protoplasm. This name had been used in 1840 by Purkinje for animal substance, but Von Mohl first brought it into general use. Presently naturalists began to suspect that the sarcode of the zoologists and the protoplasm of the botanists are essentially identical in nature. This was definitely maintained by Cohn in 1850. In 1860 Max Schultze placed the matter on a secure basis, and applied the term protoplasm to all living substance, either animal or vegetable. This led to what is known as the protoplasm-theory, which absorbed the cell-theory of Schleiden and Schwann. By Max Schultze the cell was defined as a mass of protoplasm surrounding a nucleus. Although protoplasm is so similar in appearance and reactions in all living beings, nevertheless, there must be unperceived differences — possibly not of kind but of degree of modification. See Cell-Doctrine.
Protozoa (prō′tō̇-zō′ȧ), the simplest animals. Collectively, they form the sub-kingdom of protozoa. They are microscopic and unicellular, and abound in stagnant water. They are of great interest to zoologists and physiologists, because in them the processes of life are reduced to their simplest expression. By studying them many facts are obtained that help in understanding the more complex animals. They have recently been studied in reference to their reactions to stimuli, and many important results obtained. The daily life of a protozoön was made the subject of study in one of our laboratories of physiology. The group includes simple forms like the amœba and its relatives, having root-like feet and constituting the class of Rhizopoda. Many of the rhizopods have no covering, but others either secrete a shell or gather hard particles and build one. Chalk is largely made of minute, limy shells of protozoa. The form most common in chalk is a cluster of globular chambers, varying in size. The walls of these shells are perforated by minute holes, through which the soft protoplasm of the animal protrudes. They constitute an order called foraminifera or hole-borers. These animals are abundant in warm and temperate seas. They live near the surface and, as they die, their shells sink and reach the bottom. Deep-sea explorations have brought from great depths a soft ooze, formed almost entirely of these shells of foraminifera. Somewhat similar forms make shells of great beauty, of quartz or silica, which cannot be dissolved by acid or melted by fire. They constitute the order of Radiolaria. The higher protozoa belong mainly to the class of Infusoria (which see). These minute animals have hair-like processes (cilia), which propel the body through the water like the action of many small oars. In some forms the hair-like threads are large, reduced in number to one or two and called flagella. Thus the class of infusoria is separated into the two divisions of the Flagellata and the Ciliata. The latter contains the highest developed of the protozoa. Among the more common forms may be noted the slipper-animalcule (Paramœcium), with a free-swimming, slipper-shaped body; the bell-animalcule (Vorticella), with a bell-shaped body anchored by a stalk; and the trumpet-animalcule or stentor. The rhizopoda and the infusoria are the chief classes; two others of less importance are recognized. See Leidy's Freshwater Rhizopods of North America, beautifully illustrated, published by the United States government; and Kent's Manual of the Infusoria.
Provençal (prō′vŏn′sal′) Language, The, is one of the so-called Romanic languages, all of which are descended from the language of ancient Rome. Wherever Roman
