DISEASES OF THE PEAR TREE ] 237 



in the shape of grey vescicles as large as a pin's head, or 

 larger blisters formed by the coalescence of several 

 vescicles, which eventually break open exposing the tissues 

 of the bark and wood, which are found to be in a diseased 

 condition, with black and hard concretions, resolving 

 themselv r es into a black powder. The disease (Italian^ 

 rognd] is due to a fungus Fusicladium dendriticum F'uck. 

 The diseased twigs and branches succumb sooner or 

 later, and a bad attack may result in the death of the tree. 

 The same fungus attacks also the leaves, causing 

 numerous small irregular, black spots on both sides of the 

 leaf. The diseased leaves soon turn yellow and drop off 

 leaving a bare twig which may also become a prey to the 

 disease, although the vescicles above mentioned usually 

 develop on the base of the twig or on wood more than a 

 year old Fmuladium dendriticum is generally considered 

 as the conidial form of Venturia cklorospora Ces., the 

 perithecia of which develop on the leaves in autumn. 

 This last is therefore the maturer form of the fungus, but 

 so far has escaped detection in local orchards. 



Another fungus, Fusicladium pirinum Fuck, attacks 

 the leaves and the fruit. On the leaves it produces 

 irregular broad black spots on both sides of the leaf, and 

 generally attacks the foliage when quite young, causing 

 it to drop off soon after. The same black spots varying 

 in size from a pin's head to i or 2 c.m. in diameter are 

 formed also on the green fruit (lta\ia.n = drmone or ticchio- 

 latura. re\\c\\ tavelure. Maltese = /<?<^#). The di- 

 seased fruit remains on the tree and eventually ripens, 

 the diseased spots retaining their black colour, surrounded 

 by a whitish margin of hardened tissues. In some cases 

 the spots if too small disappear at maturity, but their 

 site is always recognisable in the ripe fruit by a hardening 

 of the tissues, which usually acquire a bitter taste. On 

 trees growing in the shade or in cool situations the fruit 

 attacked by this disease becomes deeply fissured, particu- 

 larly when the disease takes the shape of minute small 



