Drosera Rotundifolia L.

DROSERA ROTUNDIFOLIA L IA ., rosyanka, family Droseraceae, herbaceous plant occurring in peat bogs (Europe, Asia). Leaves are basal, arranged in a rosette, have an oval shape and long petioles. The flowering stem is usually naked. The leaf blade is covered on the upper side with irritant sticky hairs. The plant is carnivorous: the hairs of the sundew secrete an acidic juice which can digest proteins. Rees and Will (1875) extracted a peptonizing enzyme from the leaves of the sundew and showed that it is capable of digesting fibrin. The herb of the sundew (Herba Droserae) has long been known as a folk remedy: it is applied externally to eradicate warts, internally against bronchial catarrh; for inflammatory conditions of the eyes; as a diaphoretic and diuretic and for arteriosclerosis. The dose of sundew extract is 0.1–0.3 and of tincture 0.4–2.0. ABOUT ROSOPHILA, fruit fly, genus of flies of the family Drosophilidae, embracing small, dark or variegated flies with a relatively simple wing venation system. Males are easily distinguished from females by the more rounded end of the abdomen with darker rings on the underside of the body. The genus D. contains more than 200 species described in different parts of the world. The most numerous species are in East India and on the Hawaiian Islands; in North America there are about 30 species. The species are sharply separated by characters, which is probably explained by the absence of interspecific crosses. Recently, D. melanogaster (formerly ampelophila) has become widely known due to a series of genetic works performed on this object. However, other species—D. simulans, obscura, funebris, virilis, etc.—have also been used by geneticists. At present, there is already extensive literature on the genetics of D. A detailed description of D. melanogaster is given by Sturtevant. D. melanogaster is a cosmopolitan, in the USSR it rises from the south to the Leningrad province. In laboratory conditions it is easily bred on bananas, pears, raisins, etc., with agar-agar. Usually the food is prepared as follows: 2 g of agar-agar is dissolved in 100 g of water, the water is boiled, and 50 g of raisins and 50 g of grated potato are added to it. The resulting mash is boiled for a few minutes. This mixture is poured in a layer of 1.5–2 cm into test tubes or small jars, where it solidifies, after which the surface of the food is moistened with a layer of diluted yeast, and a piece of paper is placed on top. The jar is plugged with cotton. The flies transferred there develop perfectly, giving a new generation every 10–14 days (at 20–25°). The limiting temperature for D. is 31°. For examining flies under a lens they are shaken into an empty jar plugged with cotton moistened with ether, where the flies fall asleep very quickly and remain in a narcotized state for 10–15 minutes, which does not affect their viability. Before genetic studies on D. melanogaster, a number of works were performed on the question of the influence of external agents on various traits. Thus, Carpenter in 1905 studied the change of D. melanogaster under the influence of light, gravity and other irritants. In 1906 a series of works (Castle, Cary, Clark, Mast, Barrow) on the influence of inbreeding, i.e., consanguineous crossing, mainly between brothers and sisters ("intra-breeding"), on the fertility of D. melanogaster were published. In the following years, works by Delcourt and Hennig on various anomalies in Drosophila melanogaster appeared in print, and later—works by the same authors on the influence of various factors on the development of Drosophila. And finally in 1910 the classical works of Morgan and his school begin a new era of discoveries on D. melanogaster. Careful study established that in laboratory conditions in cultures of Drosophila flies with new traits, which they did not have before, appear from time to time, and that these traits are hereditary. Later, in 1927, the Moscow geneticist S. S. Chetverikov proved that the same phenomenon is observed in natural conditions. Morgan's laboratories managed to study genetically more than 300 different hereditary traits relating to the most different parts of the body, such as: shape and color of wings and eyes, presence and absence of bristles, etc. Often the traits are imperceptible to the eye and are expressed in reduced viability, while others cause the death of the flies. The study of the inheritance of individual traits in D. melanogaster led Morgan's school to important general conclusions. It was established that, considering the change of a trait as the result of a change in a certain place in the chromosome, it is possible, on the basis of crosses, to determine this place for each trait and distribute them in a linear order. The discovery of the linear arrangement of genes in D. melanogaster served as an impetus for the study of the chromosome plan in other animals, as well as in plants. Further analysis of crosses in D. melanogaster allowed the discovery of a number of the most interesting phenomena in the chromosomal apparatus, such as an increase in the number of chromosomes, the loss of individual sections, the rearrangement of pieces of chromosomes, etc. The brilliant successes of work with D. are largely due to the simplicity of the chromosomal apparatus. D. melanogaster has 4 pairs of chromosomes, different in appearance. Males differ from females by the presence of a Y-chromosome instead of one of the two X-chromosomes. Different species of the genus D. have different sets of chromosomes, which made it possible to analyze a number of problems of comparative genetics. In 1927, Muller made epoch-making discoveries on the possibility of obtaining a large number of artificial mutations by the action of X-rays on D. The dose used by him was 50 kW, 5 mA, an aluminum filter of 1 mm, the distance of the anticathode 16–17 cm, a Coolidge tube, exposure time 12–24–48 and more minutes. Experiments were repeated with the same success by Weinstein, Serebrovsky and others. Henson obtained the same results from the action of radium. At present, a number of scientists in different parts of the world are engaged in the genetics of D. In the USSR, work on the genetics of D is conducted in the following places. Leningrad University (genetic laboratory), Moscow Institute of Experimental Biology, Zootechnical Institute, Zoo, Nazarevo-Anikovskaya Genetic Station. In addition, D. works in Germany (Berlin, Kaiser Wilhelm Inst.), in America (Texas University, Dep. of Zoology; Pasadena, California Inst. of Technology; New York, Station Exper. Evolut.) and in Norway (Oslo, Universitet Anatomisk Institut).

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