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 hypna). 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.”’ 7: 
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) “phyco” 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- 
zum). 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 
