Fungi: Their Nature and Uses

by M. C. Cooke

We cannot follow him through all the details of the growth and development of the disease, or of his experiments on this and allied species, which resulted in the affirmation that the mould immediately determines the disease of the tubercles as well as that of the leaves, and that the vegetation of the Peronospora alone determines the redoubtable epidemic to which the potato is exposed.[d] We believe that this same observer is still engaged in a series of observations, with the view, if possible, of suggesting some remedy or mitigation of the disease.

Dr. Hassall pointed out, many years since, the action of fungous mycelium, when coming in contact with cellular tissue, of inducing decomposition, a fact which has been fully confirmed by Berkeley.

Unfortunately there are other species of the same genus of moulds which are very destructive to garden produce. Peronospora gangliformis, B., attacks lettuces, and is but too common and injurious. Peronospora effusa, Grev., is found on spinach and allied plants. Peronospora Schleideniana, D. By., is in some years very common and destructive to young onions, and field crops of lucerne are very liable to attack from Peronospora trifoliorum, D. By.

The vine crops are liable to be seriously affected by a species of mould, which is but the conidia form of a species of Erysiphe. This mould, known under the name of Oidium Tuckeri, B., attacks the vines in hothouses in this country, but on the Continent the vineyards often suffer severely[e] from its depredations; unfortunately, not the only pest to which the vine is subject, for an insect threatens to be even more destructive.

Hop gardens suffer severely, in some years, from a similar disease; in this instance the mature or ultimate form is perfected. The hop mildew is Sphærotheca Castagnei, Lév., which first appears as whitish mouldy blotches on the leaves, soon becoming discoloured, and developing the black receptacles on either surface of the leaf. These may be regarded as the cardinal diseases of fungoid origin to which useful plants are subject in this country.

Amongst those of less importance, but still troublesome enough to secure the anathemas of cultivators, may be mentioned Puccinia Apii, Ca., often successful in spoiling beds of celery by attacking the leaves; Cystopus candidus, Lév., and Glæosporium concentricum, Grev., destructive to cabbages and other cruciferous plants; Trichobasis Fabæ, Lév., unsparing when once established on beans; Erysiphe Martii, Lév., in some seasons a great nuisance to the crop of peas.

Fruit trees do not wholly escape, for Rœstelia cancellata, Tul., attacks the leaves of the pear. Puccinia prunorum affects the leaves of almost all the varieties of plum. Blisters caused by Ascomyces deformans, B., contort the leaves of peaches, as Ascomyces bullatus, B., does those of the pear, and Ascomyces juglandis, B., those of the walnut. Happily we do not at present suffer from Ascomyces pruni, Fchl., which, on the Continent, attacks young plum-fruits, causing them to shrivel and fall. During the past year pear-blossoms have suffered from what seems to be a form of Helminthosporium pyrorum, and the branches are sometimes infected with Capnodium elongatum; but orchards in the United States have a worse foe in the “black knot,”[f] which causes gouty swellings in the branches, and is caused by the Sphæria morbosa of Schweinitz.

Cotton plants in India[g] were described by Dr. Shortt as subject to the attacks of a kind of mildew, which from the description appeared to be a species of Erysiphe, but on receiving specimens from India for examination, we found it to be one of those diseased conditions of tissue formerly classed with fungi under the name of Erineum; and a species of Torula attacks cotton pods after they are ripe. Tea leaves in plantations in Cachar have been said to suffer from some sort of blight, but in all that we have seen insects appear to be the depredators, although on the decaying leaves Hendersonia theicola, Cooke, establishes itself.[h] The coffee plantations of Ceylon suffer from the depredations of Hemiliea vastatrix, as well as from insects.[] Other useful plants have also their enemies in parasitic fungi.

Olive-trees in the south of Europe suffer from the attacks of a species of Antennaria, as do also orange and lemon trees from a Capnodium, which covers the foliage as if with a coating of soot. In fact most useful plants appear to have some enemy to contend with, and it is fortunate, not only for the plant, but its cultivators, if this enemy is less exacting than is the case with the potato, the vine, and the hop.