ASCOMYCETES; SACCHAROMYCETES 645 



of rye and other grasses. Many species of Peziza have a peculiar 

 form known as the botrytis form, reproduced by conids only, and 

 long believed to be altogether distinct from the Ascomycetes. Of this 

 nature is the so-called Botrytis bassiana (fig. 481), a kind of mould, the 

 growth of which is the real source of the disease termed musccvrdine 

 which formerly carried off silkworms in large numbers, just when 

 they were about to enter the chrysalis state, to the great injury of 

 their breeders. The plant presents itself under a considerable 

 variety of forms (A-F), all of which, however, are of extremely 

 simple structure, consisting of elongated or rounded cells, connected 

 in necklace-like filaments, very nearly as in the ordinary ' bead- 

 moulds.' The spores of this fungus, floating in the ah-, enter the 

 breathing-pores which open into the tracheal system of the silk- 

 worm ; they first develop themselves within the air-tubes, which 

 are soon blocked up by their growth ; and they then extend them- 

 selves through the fatty mass beneath the skin, occasioning the 

 destruction of this tissue, which is very important as a reservoir of 

 nutriment to the animal when it is about to pass into its chrysalis 

 condition. The disease invariably occasions the death of the grub 

 which it attacks ; but it seldom shows itself externally until after- 

 wards, when it rapidly shoots forth from beneath the skin, especially 

 at the junction of the rings of the body. Although it spontaneously 

 attacks only the larva, yet it may be communicated by inoculation 

 to the chrysalis and the moth, as well as to the grub ; and it has 

 also been observed to attack other lepidopterous insects. A careful 

 investigation of the circumstances which favour the development of 

 this disease was made by Audouin, who first discovered its real 

 nature ; and he showed that its spread was favoured by the over- 

 crowding of the worms in the breeding establishments, and parti- 

 cularly by the practice of throwing the bodies of such as died into a 

 heap in the immediate neighbourhood of a living silkworm ; for this 

 heap speedily became covered with this kind of mould, which 

 found upon it a most congenial soil ; and it kept up a continual 

 supply of spores, which, being diffused through the atmosphere of 

 the neighbourhood, were drawn into the breathing-pores of indi- 

 viduals previously healthy. The precautions obviously suggested by 

 the knowledge of the nature of the disease, thus afforded by the 

 microscope, having been duly put in force, its extension was success- 

 fully kept down. A similar growth of different species of the genus 

 Xphcwia takes place in the bodies of certain caterpillars, in ISTew 

 Zealand, Australia, and China ; and being thus completely pervaded 

 by a dense substance, which, when dried, has almost the solidity of 

 wood, these caterpillars come to present the appearance of twigs. 

 with long slender stalks that are formed by the growth of the fungus 

 itself. The Chinese species is valued as a medicinal drug. 



Some forms of Ascomycetes, such as the genus Tuber, to which 

 the truffle belongs, are formed completely underground. 



The Saccharomycetes are now generally regarded as a degraded 

 form of the Ascomycetes. They resemble the Schizomycetes in the 

 simplicity of their character and in their ' zymotic ' action. The most 

 familiar form of this family is the Saccharomyces (Torula) cerevisict 1 ., 



