FUNGUS OF SENECIO DISEASE
Uredo senecionis
At A is illustrated a fragment of a leaf of Senecio pulcher, natural size, and covered with the orange-coloured fungus; at B a small part of a Uredo pustule as seen bursting through the cuticle of the Senecio leaf.
No remedial measures for the extirpation of this fungus are known, but as garden Senecios and Cinerarias are infected by diseased plants of Wild Groundsel, it is desirable that plants of the latter (especially when diseased) should be destroyed. Weeds in and about gardens are a common cause of disease in cultivated plants. It often happens that a weed, being sturdy, is only slightly inconvenienced when attacked, whilst a cultivated plant will speedily succumb if attacked by the same fungus. This is the case in the Sempervivum disease. In this country the common House Leek is the nurse-plant, and is seldom much injured; but if the disease Endophyllum sempervivi gets among greenhouse species, every plant may be utterly destroyed.
FUNGI OF GLADIOLI, LILIES, ETC.
Urocystis gladioli and Ovularia elliptica
Gladiolus, Crocus, Narcissus, and Lily Diseases.—In certain soils and situations where the ground is heavy and the atmosphere inclined to be humid the Gladiolus is very subject to a destructive fungoid disease. This is especially the case during unusually wet summers. The disease attacks the corm, and corrodes and decomposes the tissues, so that on cutting open a corm the whole interior, or such parts as are diseased, will be found permeated with a deep, foxy colour. It is believed by some persons that one stage of this disease is identical with the disease named ‘Tacon’ by the French, and in this country known as ‘Copper Web,’ Rhizoctonia crocorum. This Rhizoctonia is a mere spawn or mycelium, a mass of rusty-brown material like a thick coating of spider’s web of a red tint. This parasite attacks the Crocus (especially C. sativus), the Narcissus, Asparagus, Potato, and other plants. Immersed in the softer and damper portions of the red substance of the corm may frequently be found great numbers of large compound spores, as illustrated at A (enlarged two hundred and fifty diameters). These bodies belong to the fungus named Urocystis gladioli; but whether they really belong to the spawn named Rhizoctonia there is no conclusive evidence, as the spores have never been seen on the threads or upon any spawn. The spores are very ornamental objects, consisting of from three to six compacted inner brown bodies, surrounded by an indefinite number of transparent cells. At maturity these spores break up as at B, and are the means of reproducing the fungus.
The Colchicum is attacked by a closely allied but different species of Urocystis—viz. U. colchici. The Ranunculaceæ are attacked by another ally in U. pompholygodes and Rye is attacked by a third in U. occulta. No method of cure has yet been published for this pest; it is, however, desirable that only sound and good corms should be planted, for if infected corms are placed in the ground it is one certain means of propagating the disease. The bars shown across the illustration of this disease are magnificent crystals, very common in Gladiolus corms.
Lilies are very subject to a disease in early summer: the leaves get spotted and damp, and rot off; the flower buds speedily follow, and leave the bare stalk. The disease of Lilies is caused by a fungus closely allied to the fungus of the Potato disease, and named Ovularia elliptica, known also as Botrytis elliptica (see illustration C). The spores are large, and produce zoospores, or spores with hair-like tails (cilia), capable of swimming about in water or upon moist places. This pest attacks a large number of species of Lilium, both before and after flowering. Hyacinthus candicans and some Tulips suffer from a very similar, if not the same, organism. This fungus has been described as a true Peronospora. Bulbs are subject to many fungus growths as Volutella hyacinthorum, Didymium Sowerbei, &c.; many fungi follow the decay of the bulb, others undoubtedly produce or greatly accelerate decay. No remedy is known, but we advise the purchase of the soundest and best bulbs. Good drainage and sufficient air are indispensable. All infected foliage and stems should be burned.
Disease of Hollyhocks and Malvaceous Plants.—In some parts of England the cultivation of the Hollyhock had at one time quite ceased owing to the attacks of a microscopic fungus named Puccinia malvacearum. In gardens and nurseries, where years ago Hollyhocks were one of the chief ornaments of the place, it became impossible to grow a single plant. The disease is not confined to the Hollyhock, for it attacks many malvaceous plants, notably the Mallows of our hedgesides. We have seen plants of the white variety of the Musk Mallow (Malva moschata) totally destroyed by this parasite. The home of the Hollyhock fungus is Chili, whence the Potato fungus reached us. The Hollyhock fungus first attacked the malvaceous plants of Australia, and then reached England in 1873 by the continent of Europe. The best and cleanest seeds of the Hollyhock should be purchased.