INJURIES INDUCED BY PLANTS 103 



Black-knot of Stone-fruit Trees. Although this disease has 

 hitherto been met with abundantly only in North America, still 

 it may find a place here, because experience has taught that 

 the diseases of cultivated plants may be very easily transported 

 to us from other parts of the world. It makes its presence 

 known by the occurrence on the twigs, of plums and cherries, of 

 hemispherical swellings, which project to about f of an inch and 

 are usually congregated in groups. 



The surface of the swellings is covered by the gonidia of 

 the parasite. The ascophores, which ripen in January, are in 

 the form of round prominent black capsules. The twigs that 

 are beset with knots should be removed as completely as possible 

 and burned. 



Physalospora Bidwellii is a parasite of the vine which has 

 been constantly spreading in France since 1885. The disease, 

 which is known as " Black-rot," is usually confined to the 

 berries, the young tendrils and stalks of the bunches being 

 attacked only in exceptional cases. It makes its appearance 

 a short time before the grapes ripen, when it may be recognized 

 by the appearance of a small round sooty blotch, which on 

 enlarging assumes a reddish colour, getting more intense towards 

 the centre. In a day or two the berry is entirely destroyed, and 

 three or four days later it assumes a dark colour and becomes 

 perfectly withered. The skin and succulent tissues become 

 wrinkled and shrunk and adhere to the seeds, without, 

 however, showing any wounds. Thus it is not a case of 

 decomposition but of withering. Gradually but slowly the 

 disease spreads from bunch to bunch and grape to grape. Its 

 occurrence would appear to depend on a high temperature and 

 a humid atmosphere. 



The perithecia, pycnidia, and spermogonia of this parasite are 

 known. The fungus survives from one year to another by 

 means of stylospores which are contained in the pycnidia, and 

 also by means of sclerotia. 



Coniothyrium diplodiella, a fungus which attacks the vine, is 

 only known in the form of pycnidia. The disease which it induces 

 has occurred as an epidemic in Italy, France, and Switzerland. 

 The fungus for the most part attacks the branches of the raceme 

 and the stalks of the berries, and these parts frequently become 



