CHAPTER XVII 



The Structure and Reproduction of the Fungi 



The Alga; are not the only plants in which the body is a thallus 

 of relatively simple construction, but the remaining representa- 

 tives of the Thallophyta, the lowest class of the Vegetable King- 

 dom, are characterised by the absence of chlorophyll. They are, 

 consequently, like the colourless saprophytes and parasites among 

 higher plants, dependent upon organic material elaborated by 

 other organisms. The plants in question are grouped as Fungi and 

 show many peculiarities, both in vegetative structure and the 

 nature of their reproductive processes. 



A considerable number derive all their nourishment from 

 other living plants or animals, such parasites, exemplified by the 

 Smut of Wheat, the Gooseberry Mildew, the Potato Blight, the 

 Salmon and Silkworm diseases, often doing serious harm to their 

 host. Numerous Fungi, however, live upon decaying organic 

 matter {e.g. many Moulds and Toadstools), and these saprophytes 

 play an important part in nature in connection with processes 

 of decay. 



The plant-body is of a peculiar type, consisting generally of 

 a loose weft, the mycelium (Fig. 125, a), composed of very delicate 

 branched threads or liyphcr, which are usually colourless, and 

 which may or may not be septate (Fig. 129, a). The narrow 

 diameter of the hyph^e facilitates their penetration either into 

 the interior of a host (parasites), or between the particles 

 of decaying organic material (saprophj'tes). The hyph;e, more- 

 over, secrete at their tips various cnz3'mes (cf. p. 53), which 

 bring about solution of the obstructing cell-walls and also convert 

 the organic material into a readily assimilated form, a single 

 species of Fungus producing a number of different enzymes, 



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