642 FUNGI 



which often swells to a considerable size, and its outer coat be- 

 comes frequently beautifully covered with warts or other protu- 

 berances. After a period of rest the zygospore germinates, its 

 inner coat of cellulose bursting through the outer warty and 

 cuticularised epispore, and developing into the first germinating 

 filament. 



Very nearly allied to the Mucorini are the Entomophthorese, 

 parasitic fungi, the mycele of which develops within the bodies of 

 living insects, especially caterpillars and flies, and after death 

 spreads outside the body as a flocculent felt. An example of this 

 family of fungi is frequently presented in the destruction of the 

 common house-fly by Empusa muscce. In its fully developed con- 

 dition the spore-bearing filaments of this plant stand out from the 

 body of the fly like the ' pile ' of velvet, and the spores thrown off 

 from these in all directions form a white circle round it, as it rests 

 motionless on a window-pane. The filaments which show them- 

 selves externally are the fructification of the fungus which occupies 

 the interior of the fly's body, and this originates in the spores 

 which find their way into the circulating fluid from without. A 

 healthy fly shut up with a diseased one takes the disease from it by 

 the deposit of a spore on some part of its surface ; for this, beginning 

 to germinate, sends out a process which finds its way into the 

 interior, either through the breathing-pores or between the rings 

 of the body ; and, having reached the interior cavities, it gives oft 

 the germinating filaments which constitute the earliest stage of the 

 Empusa. Again, it is not at all uncommon in the West Indies to 

 see individuals of a species of Polistes (the representative of the 

 wasp of our own country) flying about with plants of their own 

 length projecting from some part of their surface, the germs of 

 which have probably been introduced (as in the preceding case) 

 through the breathing-pores at their sides, and have taken root in 

 their substance, so as to produce a luxuriant vegetation. In time, 

 however, this fungus growth spreads through the body and destroys 

 the life of the insect ; it then seems to grow more rapidly, the 

 decomposing tissue of the dead body being still more adapted than 

 the living structure to afford it nutriment. 



The Ascomycetes include an enormous number of species, most 

 of which are parasitic on living, or saprophytic on decaying leaves, 

 many of them microscopic. The mycele always consists of branched 

 and septated hyphse. In only a comparatively few species is a 

 .sexual mode of reproduction known ; the special character of the 

 group is the non-sexual reproduction of ascospores within elongated 

 sacs or tubes known as asci. These are commonly collected together 

 in masses ; the collection of hyph?e which give birth to the asci is 

 known as the kymeni/wn, the mass of tissue enclosing or bearing the 

 hymenia as the receptacle or fructification. Its form and structure 

 vary greatly in the different sections of the family. The ascospores 

 are always produced within the ascus by free-cell formation, and 

 their number is almost always four or a ; power ' of four, most com- 

 monly eight, occasionally less than four. The asci are usually 

 surrounded by enlarged club-shaped or sterile hyphse, the para- 



