32 DISEASES OF TROPICAL PLANTS CH . 



The reproduction is both non-sexual and sexual : in 

 the non-sexual method the conidia spores are borne on 

 the surface, while in the sexual method the spores are 

 borne in delicate membranous sacs called asci. The asci 

 contain eight spores usually, and are collected into well 

 defined bodies known as ascocarps. Many species are 

 saprophytic but a very large number are parasitic and 

 are the causes of a great variety of diseases among 

 plants. 



The Fungi Imperfecti are frequently included under 

 the Ascomycetes, although it is well known that many 

 species do not belong to this group. The Fungi 

 Imperfecti are so called because we do not understand 

 their life-history and development. It is very probable 

 that the life-history of some species is truly imperfect, 

 but in many cases the students of this subject have been 

 unable to learn the facts and therefore cannot tell where 

 the species should be placed (see page 52). 



3. The BASIDIOMYCETES (Basidial Spore Fungi) are 

 far more complicated in their structure than either of the 

 preceding. They are subdivided into two groups. The 

 lower Basidiomycetes, which are parasitic on plants and 

 include the rusts and smuts ; and the higher Basidiomy- 

 cetes, which are primarily saprophytes and include the 

 puff balls and mushrooms. 



Phycomycetes 



This class is subdivided into three sub-classes as 

 follows : 



Sub-class 1. Archimycetes. In which the organisms 

 consist of little or no mycelia, and in which the sexual 

 method of reproduction is rare. 



Sub-class 2. Zygomycetes. - - The members of this 

 group have irregular, branching mycelium, non- sexual 

 reproduction by conidia or sporangia, and sexual repro- 

 duction by the union of two equal similar bodies which 

 are also known as gametes. 



Sub-class 3. Oomycetes. The organisms of this sub- 



