133 



decomposed and broken up into simpler compounds. Thus 

 only 5 per cent, of the sugar may be actually used as food 

 while 95 per cent, is reduced to alcohol and carbon dioxide. 



Other interesting plants belonging to this group are 

 the species of Meliola which form sooty black patches of mould 

 on the leaves of various trees, e.g. the Sal, Mango^and Orange. 

 The mycelium is entirely superficial and does not penetrate 

 the leaves, the fungi living on the sweet juices excreted by 

 aphides, scale and other insects. These fungi, unless excep- 

 tionally numerous, do very little harm to the trees. Preven- 

 tive measures should aim at destroying the insects. 



Rosellinia bunodes is a species which has been found to 

 be very destructive to forest trees, such as Litsaea angusti folia, 

 Schleichera trijuga and others, in Mysore and Assam. 



The roots are first attacked and the fungus is best recog- 

 nised by the clusters of small, round, black perithecia, con- 

 taining the asci, which appear at the base of the attacked stems 

 just above the ground surface. These perithecia have a car- 

 bonaceous structure and appearance and can be crushed in 

 the fingers like fragments of coal. 



119. Basidiomyceles. This' group 

 includes the most highly developed forms of fungi among mycetes. 

 which are those commonly known as Mushrooms and Toad- 

 stools. The hyphse are septate. There is no sexual repro- 

 duction. The asexual spores are developed on elongated, 

 club-shaped, terminal cells of the hyphse, which are called 

 basidia. These basidia are usually placed close together, side 

 by side, and form the hymenium or hymenial layer. At the 

 top of each basidium are situated four spores, each on a little 

 stalk. This hymenial layer may be smooth and flat, it may 

 cover the sides of thin lamellae or gills, it may line the 

 interior of pores or tubes, or it may cover the surface of 

 raised spikes, knobs, or irregular folds. A large number of 

 species are known to be injurious to Indian trees, of which 

 only a few can be mentioned. 



Armillaria mellea (perhaps better known as Agaricus mel- 

 leus) is a very destructive species in Europe and is believed 

 to occur in India. 



In Europe it is particularly destructive to coniferous trees. 

 It is one of the few species characterised by the development 

 of rhizomorphs from which in this case the mushroom-like 

 spore-bearing organs, or sporophores, arise. The sporophore 

 consists of two principal parts, the stalk, or stipe, and the 

 umbrella-shaped cap, or pileus. On the under-surface of the 



