. Botany for high schools. Botany. 262 GENERAL MORPHOLOGY OF PLANTS and propagate the fungus rapidly. These stages are called im- perfect. Another stage, which is the final stage in the life history, or life cycle, bears the sacs or asci (containing the spores or asco- spores) which make the characteristic fruit form of the members of the class. This stage is called the perfect stage of the fungus. It is often developed as the result of a sexual act, and thus repre- sents the sexual reproduction in the class. Many of the species, however, are believed to have lost the function of sexuality and
. Botany for high schools. Botany. 262 GENERAL MORPHOLOGY OF PLANTS and propagate the fungus rapidly. These stages are called im- perfect. Another stage, which is the final stage in the life history, or life cycle, bears the sacs or asci (containing the spores or asco- spores) which make the characteristic fruit form of the members of the class. This stage is called the perfect stage of the fungus. It is often developed as the result of a sexual act, and thus repre- sents the sexual reproduction in the class. Many of the species, however, are believed to have lost the function of sexuality and are supposed to develop the asci independently of a true fertilization. In a few^ of the simple forms the asci are scattered without order in loose wefts or knots of mycelium. In the majority of the species the asci are closely crowded into extended surfaces (forming a fruiting surface, the hymenium) or grouped in cup-shaped or globose fruit bodies partly or entirely surrounded by a special fungus tissue (apothecium), or entirely surrounded by fungus tissue {perithecium).^ In some species, the lichen fungi, the plant body is made up of an intimate association of fungus mycelium and algal cells. 423. The powdery mildews (Perisporiales). — The powdery mildews are very common and conspicuous fungi parasitic upon To THE Teacher. The practical study should include at least one of the powdery mildews. There are other members of the sac fungi which make striking examples for illustration. These can be shown by the teacher, and at his discretion may be included in the practical study where the time de- voted to the course will permit. One lichen can be studied and others com- pared. The yeast should be studied unless this has already been done in Part I. * These fruit bodies of the Ascomycetes are sometimes called ascocarps^ , sac Fig. 221. Leaves of willow, showing willow mil- dew. The black dots are the iruit bodies (perithecla) seated on the while Please n
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