. INTRODUCTION. 3 



asexual mode is usually present in most species, consisting of 

 minute, differentiated, spore-like bodies, borne at the tips of 

 special branches, and not enclosed in mother-cells or asci, 

 but naked. Such reproductive bodies are termed conidia, 

 which in many instances have been proved to reproduce the 

 fungus either directly or indirectly, as the spores produced 

 i n asci ascospores do. 



In many of the Ascomycetes the conidia and higher asco- 

 spores are produced by the same structure, the two forms of 

 reproductive bodies either appearing at the same time, or 

 more frequently the conidia appear first, the ascospores 

 being produced at a later stage. In other species the conidia 

 and ascospores are respectively borne by two morphologically 

 and organically distinct structures, which are often so dis- 

 similar in general appearance, that before the relationship 

 between the two was known they were placed in different 

 genera, or even in different families. 



As already mentioned, a marked feature in the evolution 

 of the Ascomycetes is the gradual suppression of the sexual 

 organs of reproduction, accompanied by a corresponding 

 evolution and differentiation of the sexual mode of reproduc- 

 tion. On the total disappearance of the sexual mode of 

 reproduction, we find the second great group of fungi the 

 Basidiomycetes gradually evolving through the Ustilagineae, 

 and the Uredineae, families including the well-known * bunt,' 

 ' rust,' and ' smut ' of our cereals, until finally, the character- 

 istic features of the Basidiomycetes are clearty indicated in 

 the Tremellineae, and the Thelephoreae, the most prominent 

 character being the production of naked spores that is, not 

 formed in a mother-cell at the tips of large, terminal cells 

 known as basidia ; as a rule each basidium bears four spores, 

 sometimes called basidiospores, at its apex. The basidia are 

 packed side by side, their tips bearing the spores forming 

 the free surface of the structure, the whole constituting the 

 hymenium, or spore-bearing surface. The further evolution 

 of the Basidiomycetes is most evident in connection with the 

 development of the sporophore for the two purposes of pro- 

 viding the greatest possible area of hymenium or spore- 

 bearing surface with the least possible expenditure of 

 material, and also for the most effective means of spore 

 dissemination. 



B 2 



