of grape sugar. This was determined by use of Barfold's reagent. Two milch cows fed on these roots died the second day. The symptoms were bloating, pain in the abdomen, obstinate constipation, and the prolonged vomiting of a tough yellow slime. In both cases pieces of the diseased beets were found in the first stomach along with other food, and no other reason for death was apparent. These beets (four varieties) were grown on a porous clay soil containing 5% lime and 8% humus. The soilwater level was 16 meters from the surface. The field had been very heavily dunged with stable manure.

II. THE HYACINTH (HYACINTHUS ORIENTALIS L.). 1. THE YELLOW DISEASE (1883).

(I) THE DISEASE.

(1) Author, Title of Paper, Place of Publication.-This disease was described by Dr. J. H. Wakker, as a result of investigations begun in the fall of 1881 at the request of the Algemeene Vereeniging voor Bloembollencultur te Haarlem, and was carried on in the laboratories of the University of Amsterdam. The first brief account appeared in 1883, in Botanisches Centralblatt (Bd. XIV, pp. 315-316) and forms part of a (30) Vorläufige Mittheilungen über Hyacinthenkrankheiten. The following year a more extended account was published in Dutch, (31) Het geel-of nieuwziek der Hyacinthen veroorzaakt door Bacterium Hyacinthi Wakker (Onderzoek der Ziekten van Hyacinthen, en andere bol-en knolgewassen. Verslag over het jaar 1883. Haarlem, August, 1884. 8vo, pp. 4-13, one colored plate). Two additional papers were published in Dutch, continuing and concluding the one above mentioned, (32) Onderzoek etc., Verslag over het jaar 1884. Haarlem, May, 1885, 8vo, pp. 1-11, and (33) Onderzoek etc., Verslag over het jaar 1885. Haarlem, May 1887, 8vo, pp. 1-5, and 27 to 37). These are the important papers to read and the ones which have mostly escaped mention. Finally, six years after the commencement of the investigation, Dr. Wakker published a fifth paper, entitled (34) Contributions à la pathologie végétale: I. La maladie du jaune, ou maladie nouvelle des jacinthes, causée par le Bacterium Hyacinthi (Archives néerlandaises d. Sci. ex. et nat., tome XXIII, 1889, pp. 1–25, pl. I). This paper is merely

an abstract of the earlier Dutch papers. Part of the lithographic figures in the plate are, however, new.

Remark. The papers published by Dr. Wakker in 1883 and 1884 were among the first contributions of any importance to the bacterial literature of plant diseases, but they were not, as claimed, actually the first. That honor belongs to this country, as we shall see later on when we come to take up pear blight, Prof. T. J. Burrill having published a long paper in 1880. The lack of literature and the difficulties in the way of the successful prosecution of this work at that time are well expressed in the Verslag for 1883: Als oorzaak van een plantenziekte waren Bacteriën nog slechts eenmaal en dot wel zeer kort (Prillieux Bull. d. l. soc. bot. d. Fr. 1879, p. 31 and 187) beschreven zoodat het geval van het geelziek niet alleen van praktisch, maar ook van hoog wetenschappelijk gewicht is. Is daarom het onderzoek er van zeker her belangwekkendste van alle ziekten, waarmede wij ons hier zullen bezighouden, het is ook tevens het moeilijkste omdat bij gebrek aan mededeelingen omtrent dit of een dergelijk onderwerp alles op eigen onderzoek berusten moet.

(2) Geographical Distribution.-This disease has prevailed extensively at times in the large bulb gardens in the Netherlands, where it is said by a majority of the Dutch horticulturists to be a new trouble, i. e., one that has appeared within the last ten years (31) or within the last 20 years (34). The writer of this digest has never been able to find the disease in bulbs imported from Holland, and does not remember to have seen any account of its occurrence in other parts of the world.

(3) Symptoms.-According to Dr. Wakker the first symptoms of the disease are usually in the foliar and floral organs. There is an apical browning or blackening of the leaves and scapes which color can often be traced downward into the green leaves for some distance in the form of dark stripes. The epidermis frequently ruptures longitudinally, and large irregular masses of bacterial slime exude from the rifts. The diseased parts also have a wet, unctuous appearance, and shrivel from the apex downward. Subsequently the bulbs become diseased, and clearly as a result of the preceding disease of the

foliar and floral organs. The earliest symptom of disease in the bulb consists on cross-section, of yellow dots, visible here and there in the interior of the scales or, on longitudinal section, of yellow lines which frequently extend into the plateau. From these spots, a mucilage swarming with bacteria can be obtained in drops by squeezing the scales or simply by exposing the cut bulb to the air. Sometimes the whole interior of the scale, or all of its inner or outer part, degenerates into a mass of yellow slime. If the attack is rapid, the plateau is soon invaded and the bulb rots in the ground during the fall or winter. If the progress of the disease is slow, and this is usually the case, the bulb sends up leaves and blossoms the following spring in the ordinary manner. At this time or afterwards there are distinct signs of the disease. In many cases the leaves turn yellow in lines parallel to the longer axis of the leaf. These lines begin at the base of the leaf and proceeding upward become less and less visible until they entirely disappear. In the interior of the leaf under these yellow stripes the bacterial slime is abundant and on the lower parts of the leaf it frequently finds its way to the surface, ruptures the epidermis and escapes. In such plants the bulb is always badly diseased, especially the outer scales which are the basal portion of the leaves of the previous year, and this, taken in connection with the fact that the bulbs are entirely sound in most cases where the symptoms are only visible at the apex of the leaf, renders it very probable that the latter is to be regarded as the first stage of the disease and the former as a later stage, supervening the second year. Another symptom, sometimes observed the second year, is unequal growth, i. e., a distinct curving over of the foliage toward that side of the plateau which has perished or is no longer capable of furnishing the proper supply of water and nutrient substances, the curvature being, of course, due to the one-sided growth. As a rule, diseased bulbs do not produce many bulblets, and not all of the latter are always diseased. If planted out, those which are diseased show signs of the malady in the young plants after a longer or shorter period. The leaves turn yellow, become flabby and droop, or show the characteristic longitudinal rifts in the epidermis. When such

young bulbs are cut, the plateau (central short stem of the bulb) is often found to be the only diseased part, something inexplicable if we do not admit that the disease has been transmitted to the bulblet from the mother bulb. Such is the usual form of the disease, but it will be understood that there are numerons modifying circumstances, the disease sometimes beginning lower down on the edge of the leaf, or even underground, or progressing more rapidly, the latter especially when the disease attacks full grown leaves and scapes. The most cases of the first stage of the disease are noticed in the field in May, but cases also occur much earlier in the year.

(4) Pathological Histology.—In spring, in the first stage of the disease, when only the tips of the leaves are attacked, microscopic examination shows the bacterial slime to be present in the intercellular spaces of the shrivelling leaf-parenchyma, but always only in small quantity. From this part of the leaf the bacteria may be traced long distances down the vascular bundles, but have not yet reached the bulbs, the latter being still entirely sound. In autumn, on the contrary, cross sections of the bulbs, if not too badly diseased, show numerous yellow dots in the scales, and on microscopic examination these are found to correspond to the xylem part of the vascular bundles (No. 34, pl. I, figs. 9, 10). The vessels of the latter are seen to be full of a thick, yellow slime, which often partially dissolves them. Here and there, the whole xylem part of the bundle may disappear, the yellow slime taking its place. In this way are formed continuous, tubular cavities, filled with isolated cells of the host plant, remnants of spiral threads, and an innumerable number of bacteria. In this stage of the disease, the sieve tubes are not yet attacked, but these are subsequently destroyed, and frequently, also, the parenchymatic tissues outside of the bundles, the substance which unites the cells being first dissolved. The second spring, a microscopic examination of the yellow striped leaves from diseased bulbs shows a similar occupation of the vessels with the same lesions, but in a reverse order, the bacteria being most abundant and the destruction of tissues greatest in the basal part of the leaf. Here the bacteria dissolve the walls of the vessels

and make their way into the surrounding tissues, first isolating and then destroying the parenchymatic cells and finally increasing to such an extent that the epidermis is ruptured and a viscid, yellow ooze escapes. The vessels of the scape are filled in the same way, but the bacterial slime was not observed in the roots. The bacteria may be distinguished in the vessels considerable distances in advance of any external or macroscopic symptoms. The bacterial mucilage is a yellow liquid, thick and viscid. Under a low power of the microscope it shows a granular structure, this being due, as we recognize on higher magnification, to the presence of bacteria. Dr. Wakker describes at some length his method of examination "The transverse sections must be made with extreme care, such as is almost unknown in the ordinary study of vegetable anatomy. Not only is the affected tissue so soft that it is impossible, in a fresh state, to cut sections sufficiently thin, but there is also danger that the mucilage will be dragged by the knife into parts of the leaf where originally there was not a trace of it. To overcome these two difficulties good use was made of absolute alcohol. The green color was removed by this method while the yellow of the mucilage persisted, and, in consequence, became much more distinct, so that it was easier to distinguish diseased from healthy tissues.”

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(5) Direct Infection Experiments.-This disease was studied before Koch's plate method of isolation had come into general use, and most of the infection experiments were made directly from diseased to healthy plants. In the fall of 1882 bacteria were introduced into a bulb of the double white Anna Maria, and when this bulb was cut the next spring it showed distinct signs of the disease. This experiment was frequently repeated and always with the same result. For example, the whole cut surface of the scales of a bulb from which roots and leaves were cut away in summer was smeared with the bacterial slime, and in 14 days the disease was to be found in the vascular bundles of the youngest scales, and shortly after in those of the older. Slightly diseased bulbs are the best parts from which to obtain the bacteria. In badly diseased plants one runs the danger of finding all sorts of things, even Penicillium, in the de