PLANT DISEASES. "WILD PLANTS AS A SOURCE OF DANGER. 937 



and causing an epidemic disease. Eutypella pruni has long been known 

 to botanists as a parasite on various wild species of Prunus, specially the 

 Sloe or Blackthorn (see figure, Journal, xxvi. p. 742). During the last 

 few years, however, it has found its way into gardens, and is now attack- 

 ing Apples, Pears, Plums, Peaches, and other rosaceous trees. Specimens 

 have been received at Kew during the past summer from various parts of 

 England, and reports show that its invasion into orchards is becoming 

 general, and that it is working dire havoc amongst young trees, especially 

 those on a clay soil. (Gard. Chron. Sept. 27, 1902.) 



This is a forcible illustration of how disease on wild plants can pass 

 on to cultivated varieties, and though in the case cited some may regard 

 it as unavoidable, yet it is hoped such an instance may convince gardeners 

 of the existence of the danger, and stimulate their efforts to eradicate 

 those weeds which may be easily destroyed. Some of these latter 

 plants will now be mentioned, taking them according to their natural 

 orders. 



RANUNCULACEJE. — Several common species of Buttercups 

 (Ranunculus repens, bulbosus, and auricomus) aid in retaining the 

 disease of garden Anemones and Hellebores, known as Smut. The fungus 

 (Uromyces anemones) which causes this disease produces black sooty 

 masses on the leaves and stems, and in some seasons completely destroys 

 the beauty of the plants attacked. In combating this pest, a sharp look- 

 out should be kept for Buttercups, and if any are seen to be diseased, 

 they should not merely be hoed down and left to die, but be collected 

 and burnt, as the black sooty masses are made up of thousands of 

 minute spores. The Wood Anemone is also a common victim to this 

 disease, and if cultivated varieties are grown in the immediate vicinity of 

 these it is not astonishing that the disease spreads. A description and 

 figures of this fungus, with references to literature, will be found in 

 Dr. M. C. Cooke's " Pests of the Flower Garden " (Journal, xxvii. p. 14). 



Another disease, caused by Sclcrotinia tuberosa, is also constantly found 

 on wild Anemones. In woods, the Peziza cups (or fruits of the fungus) 

 are easily overlooked, as they are of a brown colour and hidden by the 

 Anemone foliage, and the damage they do here remains unnoticed. If 

 the disease makes its way into the garden, however, its effects are at once 

 observable by the sickly plants that result. A. japonica is mostly 

 attacked, and in some districts so badly that its cultivation has been 

 abandoned altogether. This fungus, as far as is known, only attacks 

 the genus Anemone, and where it is rampant it is advisable not to grow 

 cultivated Anemones nearer any patches of the woodland species than is 

 absolutely necessary. (M. C. Cooke, loc. cit. p. 15.) 



CRUCIFERJE.— Club Root, which is the worst disease of this order, 

 has already been noticed. 



There are, however, two others of more or less importance, that are 

 common on weeds ; both of these are white moulds which resemble in 

 external appearance the mildews. The one, Peronospora parasitica, is 

 very destructive to Wallflowers and Stocks, and also Turnips ; the 

 other, Cystopus candidus, attacks Radish, Horse-Radish, and Cabbage ; 

 young plants are chiefly attacked. Capsella bursa pastoris (Shepherd's 

 Purse) and Alliaria officinalis (Garlic Mustard) are the wild plants which 



