Root-knot eelworm.—­A dangerous insect pest which frequently attacks the Tomato, in common with the Cucumber and Melon, is the Root-knot Eelworm (=Heterodera radicicola=).  The root on which the swollen pea-like knots develop do not carry on their ordinary functions, and the leaves droop, the stem becomes limp, and the whole plant soon collapses and dies if the trouble is severe.  The treatment suggested on page 425 should be adopted.

Sometimes the outdoor Tomato crop is attacked by =Phytophthora infestans=, the fungus responsible for the Potato Disease:  Bordeaux mixture should be used to check it.

Directions for preparing the Bordeaux mixture are given on page 440.

Another useful preparation which checks many fungus diseases may be made by dissolving one ounce of potassium sulphide (liver of sulphur) in three or four gallons of water, to which should be added an ounce or two of soft soap.  The last named greatly assists in the complete and uniform wetting of all parts of the foliage.

THE FUNGUS PESTS OF CERTAIN FLOWERS

==Cineraria and Senecio Disease.==—­=Senecio pulcher=, soon after its introduction into England, was attacked, and in some gardens completely destroyed, by a fungus named =Puccinia glomerata=, or rather the =Uredo= stage of this fungus with simple, not compound, spores.  The fungus is well known, being closely allied to that which causes the rust or mildew of corn crops.  It is very common on the wild species of Groundsel in England, being especially frequent and virulent on the Ragwort Groundsel, =Senecio Jacobea=, from August to October.  The leaves of infected plants are covered with rust-coloured dusty pustules, the =Uredo= condition of the fungus, and known in this stage as =Uredo senecionis=, sometimes termed =Trichobasis senecionis=.  The fungus has a =Puccinia= stage of growth very similar to that of the Hollyhock fungus, =Puccinia malvacearum=.

[Illustration:  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.