352 THALLOPHYTES 



group. A knowledge of their plant bodies, methods of reproduc- 

 tion, and how they injure other plants is essential for working 

 out methods of controlling the destructive forms. 



The plant body of. Fungi consists of a mass of colorless branch- 

 ing threads or filaments, and is called a mycelium (plural mycelia) . 

 The individual threads are called hyphae (singular hypha) . The 

 hyphae constituting a mycelium may be loosely interwoven, 

 forming a structure resembling a delicate cobweb, as in the Bread 

 Mold, or they may be woven into a compact body having a 

 definite shape, such as occurs in Toadstools and Mushrooms. 

 The mycelium must be in direct contact with its food supply, 

 which is called the substratum. 



Sometimes, especially in the case of parasites, special short 

 branches are formed which penetrate the host and absorb food 

 material. These special absorbing branches are called haustoria, 

 meaning "absorbers." 



Hyphae are modified in various ways for reproduction. Some 

 produce spores, which are sometimes borne in sporangia and 

 sometimes openly on the end or sides of the hyphae. Some are 

 modified into organs for bearing sex cells. These various modi- 

 fications for reproduction will be learned as the different groups 

 and their types are studied. 



Divisions of Fungi. The Fungi are so much modified by 

 their peculiar life habits that they have either lost or disguised 

 the structures which prove most helpful in the classification of the 

 Algae. The Fungi are divided into four large subdivisions, but 

 the life histories of only three of the subdivisions are well known. 



The constant termination of the group names is mycetes, a 

 Greek word meaning "Fungi." To this name is added a prefix 

 which is intended to indicate some important character of the 

 group. The three subdivisions in which the life histories are 

 known are named as follows: (1) Phycomycetes (Alga-like 

 Fungi) "phyeo" coming from "phykos," meaning Seaweed and 

 suggesting the water habits of this group; (2) Ascomycetes (Sac 

 Fungi), so named because they bear spores in small sacs called 

 asci (singular ascus); and (3) Basidiomycetes, Fungi which bear 

 spores on small club-shaped hyphae called basidia (singular basid- 

 ium). To the Basidiomycetes belong such familiar forms as 

 the Toadstools, Mushrooms, Rusts, and Smuts. The fourth 

 group is known as the Fungi Imperfecti. They are those Fungi 



