DISEASES CAUSED BY FUNGI. 73 



nated with spawn before it is used. This, indeed, is almost 

 always the case where trees are grown from old stools, and 

 not from seed. The foxy oak, so common in some districts, 

 is almost entirely due to this cause ; and I have seen such 

 timber after a few years covered with Fungi to such an ex- 

 tent as to necessitate extensive repairs. 



A large quantity of Fungi prey on the tissues of living 

 leaves ; the spawn of some of these runs over the surface ; of 

 some it creeps amongst the loose tissue of the under side of 

 leaves ; while in others it is more intimately incorporated with 

 the firmer cells. 



It is not easy to describe the two first apart, as different 

 species of the same genus have different habits. The same, 

 indeed, may be said occasionally of different individuals of the 

 same species, but in either case they are capable of inflict- 

 ing great injury. The Hop Mould, the Rose Mildew, the 

 Vine Mildew, and a multitude of other allied Fungi, partly 

 by feeding on the proper juices of the plant, and partly by 

 clogging up the breathing pores, exhaust the plant and im- 

 pede its circulation and respiration. Most of these will yield 

 to sublimated sulphur, if timely and judiciously applied. The 

 conditions under which these Fungi appear is very different. 

 Some of them never perfect their true fruit, being propagated 

 by a secondary fruit analogous to the reproductive buds of 

 certain Phsenogams, as Begonice. In some there are four or 

 five distinct modes of propagation, and in consequence they 

 spread Avith frightful rapidity. The cultivation of the Vine in 

 Madeira has almost entirely ceased from this cause, and is 

 very precarious everywhere. It is curious that this Fungus 

 has never been found on the American Vines, or their nume- 

 rous varieties, even when cultivated in Europe. The Isabella, 

 for instance, a grape of American origin, has been always free 



