NATURE OF FUNGI. 7 



nourishment by means of a mycelium from the matrix,"* there 

 a*e exceptions to this rule with which the majority accord. 



Of the fungi found on animal substances, none are more 

 extraordinary than those species which attack insects. The 

 white mould which in autumn proves so destructive to the 

 common house-fly may for the present be omitted, as it is 

 probably a condition of one of the Saprolegniei, which some 

 authors include with fungi, and others with algae. Wasps, 

 spiders, moths, and butterflies become enveloped in a kind of 

 mould named Isaria, which constitutes the conidia of Torrulia, 

 a genus of club-shaped Spharice afterwards developed. Some 

 species of Isaria and Torrubia also affect the larvae and pupae 

 of moths and butterflies, converting the whole interior into a 

 mass of mycelium, and fructifying in a clavate head. It has 

 been subject for discussion whether in such instances the 

 fungus commenced its development during the life of the in- 

 sect, and thus hastened its death, or whether it resulted after 

 death, and was subsequent to the commencement of decay, t 

 The position in which certain large moths are found standing 

 on leaves when infested with Isaria resembles so closely that 

 of the house-fly when succumbing to Sporendonema MUSC&, 

 would lead to the conclusion that certainly in some cases the 

 insect was attacked by the fungus whilst still living ; whilst in 

 the case of buried caterpillars, such as the New Zealand or 

 British Hepialus, it is difficult to decide. Whether in life or 

 death in these instances, it is clear that the silk- worm disease 

 Muscardine attacks the living insect, and causes death. In the 

 case of the G-uepes vegetantes, the wasp is said to fly about with 

 the fungus partially developed. 



In all fungi we may recognize a vegetative and a reproductive 

 system : sometimes the first only becomes developed, and then 

 the fungus is imperfect, and sometimes the latter is far more 

 prominent than the former. There is usually an agglomeration 

 of delicate threads, either jointed or not, which are somewhat 

 analogous to the roots of higher plants. These delicate threads 



* Berkeley's "Introduction to Cryptogamic Botany," p. 235. 



t Gray, " Notices of Insects which form the Basis of Fungoid Parasites." 



