The diseased grafts grow vigorously the first year; in the second year they flower extraordinarily freely and bear an unusually heavy crop of fruit. Then the leaves begin to turn yellow along the midrib for a width of 3 to 5 mm. on either side. The discoloration afterward spreads to the lateral veins; the leaf has a peculiar appearance, the destruction of the chlorophyll continues, and soon the whole leaf loses its colour. This disease, which seems not to have been described yet in America, is very similar to the "infectious chlorosis of the Malvaceae of V. Baur (1906). The writer states that in practice it is easy to prevent the trees contracting this malady, which he has proved by numerous experiments to be only communicable by grafting. As M. Trabut found no traces of bacteria, he admits for the present Baur's hypothesis, according to which the disease is caused by a phytotoxin secreted by an organism which has escaped microscopic investigations, but proves its presence by the inoculation results. BACTERIAL AND FUNGOID DISEASES. 425 The Contamination of the Soil by the Toxic Products of Parasitic Fungi. PANTANELLI, E. Su l'inquinamento del terreno con sostanze nocive prodotte dai funghi parassiti delle piante. Rendiconti delle sedute della Reale Accademia dei Lincei, Classe di Scienze fisiche, matematiche e naturali, Vol. XXII, 1st Half-year, Part 2, pp. 116-120. Roma, 1913. ID. Ancora sull' inquinamento del terreno con sostanze nocive prodotte da funghi parassiti delle piante. Ibidem, part 3, pp. 170-174, fig. 1. Roma, 1913. The aim of the writer was to discover if those fungi which attack the underground portions of plants under the natural conditions of parasitism can, during their lifetime, secrete sufficient toxic matter to permeate the soil and contaminate the latter for some distance from the part of the plant attacked, or whether these furgi leave toxic substances in the infected parts, even at their death, thus contaminating the soil for a certain length of time. The first experiments were made in 1910; some sterilized wheat grains were germinated in contact with a raw or boiled in fusion of Septoria graminum or with mould derived from wheat leaves attacked by this fungus, and also in contact with soil impregnated with the same un boiled in fusion. Identical experiments were also carried out in 1910, with melou plants of which the crowns were infested by Fusarium niveum and with white mustard attacked by a species of Pleospora. An attempt was made, in the case of the mustard, to separate the toxic substances by precipitating the infusion with 30 to 45 per cent. alcohol. Similar experiments were made. in 1911, when the base of the stem of beans attacked by Sclerotinia Libertiana and of lucerne infected with Fusarium incarnatum were selected. FUNGI The results were concordant and thus showed that soil, especially if it contains clay, can be impregnated with toxic products arising from the decomposition of vegetable organs infected by fungus parasites. To avoid the objection raised, that by using entire infected organs in the previous experiments, it was impossible to be sure that the toxic matter was not derived from the cells of the host plant, pure cultures of Sclerotinia Libertiana were employed in 1911, and of Fusarium incarnatum in 1912; these were studied in connection with the germination of red clover and lucerne. In the case of the clover, the experiment clearly showed that the unboiled culture liquid (liquid gelatine) was much more injurious thau mycelium juice (the mycelium was already old), and lost some of its toxic property on heating; 60 per cent. of its insoluble components were toxic; the volcanic sand (used as a substratum), being composed of coarse crystalline particles, did not absorb any of the toxic substances; while the loam soil retained the great portion of the latter in a form which was not accessible to the roots. The extremities of the roots were wilted, brown, or completely decomposed in some cultures, and had not been able to grow more than 263 mm. in length; in another culture, they were well developed where the seed had germinated deeply, but in seeds which had germinated at the surface they were withered and brown; this shows that the toxic substances remained in the upper layer of the soil. It appears, on the other hand, that the lucerne was stimulated by some substance present in the unboiled culture; but the boiled liquid slightly hindered germination. In any case, the roots of the first seeds which germinated were arrested in their development, and their extremities were discolored or destroyed in some of the cultures; the roots of the seeds last germinated were on the contrary quite healthy. This proves that the injurious substances had already undergone some change. The effect of toxic preparations from Sclerotinia Libertiana was tried upon chickpea and lentil plants one month old grown on sterile volcanic sand. The mycelium juice produced no alterations; the neutralized unboiled culture liquid caused the death of the whole plant in one night, and if the liquid was heated to 100oC., the same effect was produced in two or three days. In a second note the writer gives an account of similar esperiments to those made with a pure culture of Scl. Libertiana; these were carried out in 1912 with a culture of Fusarium incarnatum isolated from lucerne which was much damaged. This fungus also, according to the different experiments, elaborates toxic compounds of various kinds, amongst which, in the last analyses, volatile and stable nitrogenous bases predominated; these prevent the germination of the seeds and injure the roots of various Leguminosae. It still remained to be seen whether these different fungi produce similar effects if the products are allowed to diffuse naturally in the soil. The first experiments made and carried out with suitable precautions with Fus. niveum on water-melons, Scl. Libertiana on beans and Fus. incarnatum on sainfoin and clover, proved that from the mycelia of these fungi and from their substratum, which under natural conditions would be the part of the plant attacked, toxic substances can permeate the neighbouring soil, so that they would hinder the growth of the roots, or prevent the germination of the seeds of similar plants. 426 - Revue Researches on the Disease Caused by Rhizoctonia violacea. ERIKSSON, JACOB. Études sur la maladie produite par la Rhizoctone violacée. générale de Botanique, Year 25, No. 289, pp. 14-30, figs. 1-4. Paris, 1913. After a rapid review of the history of this disease and a description of its characteristics in Sweden, where it occurs especially on carrots and beets, the writer mentions, taking previous observations as a basis, that Rhizoctonia violacea attacks a large number of host plants, which are very varied from a systematic point of view. But in going into the matter more closely, it becomes clear that in a place where several species of plants are growing the disease does not attack all with the same intensity. This parasite has a certain tendency, though a slight one, to give rise to biological races. This can be proved (as was done by the writer during the summers of 1898 to 1902 and in the summer of 1911) by parallel inoculation experiments made with infections derived from different species of plants. By this means the writer was able to prove from two series of experiments, that the propagation of the disease by means of infectious matter derived from carrots and beets respectively was much easier and more effectual, if the subjects of the inoculation belonged to the same species as those which furnished the virus, and became increasingly difficult in the case of the other plants experimentad upon in the following order: Stellaria media, Myosotis arvensis, Galeopsis Tetrahit, Erysimum cheiranthoides, Urtica dioica, Sonchius arvensis, turnip, lucerne, potatoes; while others, such as clover and parsnip, are resistant to the infection. Having recently re-examined the experimental material collected in 1898, Prof. Eriksson thinks (at least as far as the form of fungus attacking carrots is concerned) that the much debated question of the systematic position of the sterile mycelium known as Rhizoctonia violacea is now decided; its proper scientific name is Hypochnus violaceus (Tul.) Eriks. The fungus, during its vegetative period, forms upon the roots of many plants a felt-like mass of sterile mycelium, living as a parasite underground, of a reddish-violet colour and characterised by numerous confluent filaments which are septate and ramified. From this felt arise round sclerotia, dark brown in colour and resembling perithecia. This is the Rhizoctonia stage. Subsequently the fungus forms round the stems of the same plants, or of other species, and immediately above the soil, an annular membranous pale pink envelope, which often ascends the stems to a height of 5 to 15 mm., sometimes extending over the surface of the soil as a very thin sheet, and produces the basidiophores. This latter is the Hypochnus stage. The name Dauci may be given temporarily to the species-form which has its Rhizoctonia stage on the bases of the stems of Stellaria media, Myosotis arvensis, Galeopsis Tetrahit, Erysimum cheiranthoides, Urtica dioica and Sonchus arvensis. Until further experiments and researches have been made, it is impossible to decide positively if the felted mycelium found on beets (Rhizoctonia violacea sp.-f. Betae), on clover, lucerne, etc., also possesses a Hypochnus form. It is remarkable that the fruiting stage of the fungus (at least in the case of the sp.-f. Dauci) occurs on species of plants other than those infested by the sterile mycelium, and also that the fungus, which in the sterile stage is a pronounced parasite with much power of destruction, appears scarcely parasitic at all in its fruiting stage. The occurrence of the fruiting stage on species of plants other than those of the hosts of the sterile stage recalls the dioecious habit of many fungi of the rust family; in any case this Hypochnus stage requires further investigations. In conclusion, the writer mentions the following methods for the control of the disease when it attacks carrots, beets and other roots : a) At the time the crop is gathered, all stems showing the least trace of the disease should be destroyed, by cooking or otherwise. b) The spots where diseased plants have grown should be marked by rings of sticks; the infected soil should then be treated with a fungicide, e. g. carbon disulphide (1⁄2 lb. in 10 gallons of water, 8 gallons being sufficient for 15 sq. yds.). c) The roots which have been dug up from near the infected spots must be examined at intervals during the winter and all diseased ones destroyed. d) A rotation of at least 4 years should be adopted, only such plants being cultivated as cannot possibly serve as hosts to the parasite. e) The dung of animals fed on the contaminated roots must not be used as fresh manure. 427 Researches on the Development and Control of Vine Mildew. It is well known that there is considerable difference of opinion amongst investigators as to the method of germination of the oospores of vine mildew (Plasmo para viticola) in spring. MM. Ch. Richon, Farlow and P. Viala believe that the oospores set free at a particular time zoospores which probably infect the vine in the same manner as the zoospores produced by the summer conidia. Others, M. Prillieux in particular, are of opinion that the oospores send out a germ-tube, which is modified later into a true conidiophore resembling the usual fructifications of the fungus which in summer project through the stomata of the leaf. The writer, however, during the numerous researches and experiments which he made on the oospores of many vine leaves of the Chasselas variety gathered in the autumn of 1911, in no case saw any signs of a germ-tube, and was never able to infect the upper or lower surfaces of the leaves by means of oospores. The solution of the question necessitates further re search, but the writer does not think that the oospores can at all readly germinate in spring and infect the vine. During the summer of 1912, M. Faes made some further experiments on the infection of vine leaves and bunches of grapes by mildew conidia. As far as the former were concerned, these experiments confirmed his previous observations: the germ-tube issues from the zoospore and penetrates into the interior of the leaf by means of the stomata on its lower surface. In the case of the bunches, the infection of the buds takes place by means of the stomata on the upper part of the petals. The writer obtained negative results in attempting to infect the flowers after the fall of the corolla, Grapes of the size of a pea could only be infected when the conidia were placed on the point of insertion of the pedicel in the grape, or on the pedicel itself. In conclusion, the writer mentions that in 1912, all vines which were well-tended and sulphured were immune from the attacks of mildew. Comparative experiments proved that sulphuring the lower surface of the leaf in all cases protected the vines as well as sulphuring the upper surface. This subject, however, needs further investigation. 428 - Sterigmatocystis nigra damaging Tobacco in Hungary. RAPAICS, RAYMUND. A dohány kormos rothadása,- Magyar Dohanyujság, Year XXX, During the last two years, a fungus disease which had not been recorded from other countries in Europe has been causing havoc in Hungary. The fungus is Sterigmatocystis nigra, known only in North America, where it is called canker or black rot. It attacks tobacco during the fermentation and decomposes the leaves, reducing them to a black powder. In 1911, M. Étienne Uray, controller of the purchase of tobacco at Budapest, when buying tobacco for the Royal Excise Office of Hungary, discovered for the first time Sterigmatocystis nigra on the leaves. Subsequently the Experimental Station of Tobacco Cultivation at Debreczen made a chemical examination of the material and stated that this was the first time that the fungus had been observed to attack tobacco in Hungary. This new disease is the more dangerous in that the cause of the appearance of the parasite on fermenting tobacco leaves is not known, although the same fungus has been met with upon other decomposing substances. The writer gives some information on the nature of the disease, and considers that the black powdery decomposition product of the leaves which are attacked is directly due to the fungus. No efficacious remedy has so far been discovered. BACTERIAL AND FUNGOID OF VARIOUS |