2 INTRODUCTION 



their true position." With this viewpoint the author is in agreement, but 

 since most mycologists accept these organisms as fungi they are included 

 in this textbook. 



From the foregoing it is apparent that the fungi do not possess chloro- 

 phyll and also that the chlorophyll-less bacteria and Mycetozoa are ex- 

 cluded from their ranks. There are many other organisms which lack 

 chlorophyll and still are not fungi. Thus in the diatomaceous genus 

 Nitzschia some species are known that possess no chloroplasts while the 

 majority of species possess them. Otherwise they are so similar that they 

 are retained in the same genus. In the Red Seaweeds (Florideae) there 

 are several species that lack chlorophyll and are parasitic upon other 

 Florideae — e.g., Harveyella mirahilis (Reinsch) Schmitz & Reinke (see 

 Sturch, 1899). Yet in their modes of sexual and asexual reproduction 

 they can be assigned definite positions among these algae. Among the 

 higher plants (Anthophyta or Angiospermae) many widely separated 

 chlorophyll-less species are found, e.g., in the Orchidaceae and Bur- 

 manniaceae among the Monocotyledoneae, and Cuscuta, Cassytha, Mo- 

 notropa, Rafflesia, Orohanche, and many others in the Dicotyledoneae. 

 Thus it is necessary to delimit the fungi by further characters than 

 merely the lack of chlorophyll. Such a definition is in the main negative. 



Definition. As a group the fungi may be defined as chlorophyll-less 

 nonvascular plants whose reproductive or vegetative structures do not 

 permit them to be assigned to positions among recognized groups of 

 algae or higher plants, and as excluding the Bacteria (which are typically 

 one-celled and lack a typical nucleus) and the Mycetozoa (which have 

 an animal type of structure and reproduction). 



Whether the fungi represent a single phylum of organisms with a 

 common origin or have arisen in independent lines from several ancestral 

 types of plants is still a matter of debate among students of their phylog- 

 eny and classification. They range from very simple short-lived, one- 

 celled structures whose single cell becomes the organ of reproduction 

 (e.g., Olpidiopsis, which at maturity becomes the zoosporangium from 

 which escape the zoospores) to massive perennial mycelia giving rise to 

 great spore fruits as in some of the puffballs, pore fungi, etc. Except for 

 the lack of chlorophyll and the saprophytic or parasitic mode of life 

 thereby necessitated, these two extremes have no single character in 

 common: manner of reproduction, structure of the vegetative body, 

 chemical composition of the cell wall, etc. The extreme simplicity of the 

 one type of fungus might be considered to indicate a low position in 

 evolution, i.e., great primitiveness, but on the other hand it might be the 

 result of a great degree of simplification from a much more complex 

 fungus. The lack of any good fossil record of these lower fungi prevents 

 us from obtaining direct evidence in this matter. 



