The first of the diseases of which M. de Thumen speaks is the most common and well known of the three; it is a mould which is caused by the rapid development of a a mildew similar to that which affects the vine; this external growth is known to botanists by the name of Oidium leucoconium in the early stages of its development, and under that of Sphaerotheca pannosa when it has attained its mature condition. It is known that this parasite covers the roses with a white film, amid which are specks and spots of a brown color; propagates very rapidly, and its mischievous results are only too well known. On the shrubs which it attacks the flowers are either malformed or entirely abortive. All the varieties are not equally liable to this disease, but certain varieties are attacked with it every year. Happily, sulphur is an excellent remedy for mildew in roses as well as for Oidium on the vine; only, in order to be fully efficacious, the precautions which the learned German prescribes as the result of his own experience must be carefully followed. The flowers of sulphur must be employed not once only, but several times in the course of the summer.

The application of the sulphur must be made on a fine clear day; when there is every appearance of the fine weather lasting; then the work should be begun early in the morning, in order that the sulphur may be subjected to the rays of the sun for as long a time as possible. Under these conditions M. de Thumen says that he perfectly cured, last year, some infected rose trees which subsequently flowered finely.

The second disease of roses to which this observer alludes, is not so well known as the first mentioned, nevertheless for several years it has very frequently been seen in gardens. The German gardeners call it brand (burning), a vague term which is applied in Germany to many diseases of vegetables. It is caused by a little parasitical fungus, Asteroma radiosum. This parasite causes specks of a dark greenish-brown on the upper surface of the rose leaves, which are often not more than a millimetre in diameter; but which sometimes cover the whole of the leaf. Soon after the appearance of these spots the leaves fall, being in some cases still green, while in others they have become more or less yellow. Asteroma, not being confined to the surface of leaves as the mildew is, but thrusting its filaments through their tissues, the war against this parasite becomes therefore very difficult. The great attention paid to this by the well-known Berlin naturalist, Professor B. Frank, has disclosed the fact that this fungus produces a great number of excessively tiny reproductive organs; that is to say, the spores, which are dispersed and spread by the rain and dew.

This water, bearing the spores, trickles down the leaf-stalk to the base of the leaves, where it deposits them on the bud which is formed there, therefore the shoot springing from this bud is necessarily tainted with the disease, with the germs of which it was early infected. Whether the plants thus infested with the parasite are placed in another garden, or whether buds from the diseased plants are budded on healthy stocks the disease will assuredly be propagated. Thus convinced of the impossibility of dealing with the parasite, which grows chiefly in the interior, by any external remedy, M. Frank sees no other alternative but not to make any use of the gardens thus infected; but this would be a great barrier to trade. M. Thumen, on the other hand, recommends a solution of salycylic acid, which kills the spores of the parasite. In many cases he advises that the plants or grafts sent out from the nursery in which this fungus exists should be plunged for an hour in a solution of salycylic acid.

The infected leaves should be burnt immediately, and the bushes should be syringed with salycylic acid in early spring.

The third disease of roses is of less consequence. It is due to a parasitical fungus, Caeoma miniatum (Phragmidium subcorticium), which rarely appears on the leaves, but more frequently on the leaf-stalk, flower-stalk, calyx, or flower. It forms cushionlike projections of an orange-red color (AEcidium). The disease is usually not very fatal, but where it becomes so it is better to burn the infected plants. Abstract from an article in the "Wiener Illustrirte Garten Zeitung." - From Gardeners' Chronicle.