288 GENERAL MORPHOLOGY OF PLANTS 



conidia (asexual spores) which serve to multiply and propagate 

 the fungus rapidly. These stages are called imperfect. Another 

 stage, which is the final stage in the life history, or life cycle, 

 bears the sacs or asci (containing the spores or ascospores) form- 

 ing the characteristic fruit body of the members of the class. 

 This stage is called the perfect or final stage of the fungus. It is 

 often developed as the result of a sexual act, and thus represents 

 the sexual reproduction in the class.* 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,f ) or grouped in cup-shaped fruit bodies partly sur- 

 rounded by a special fungus tissue, J or entirely surrounded by 

 fungus tissue. In some species, the the lichen fungi, the plant 

 body is made up of an intimate association of fungus mycelium 

 and algal cells (paragraphs 447-453). 



436. The blue mold (Penicillium). The conidial stage (or 

 imperfect stage) of a sac fungus is well represented by the blue 

 mold, Penicillium, which is common on decaying fruits, and some- 

 times appears on preserves when they are not properly protected 

 from the air. The mycelium consists of very fine branched 

 threads which grow in the decaying substance. From this 

 mycelium numerous upright threads, or stalks, arise into the air, 

 each one producing a number of short crowded branches near the 

 tip. These short branches bear the conidia (asexual spores) at 

 their tips. Each conidium is very minute, and round. They 

 are united in chains or necklaces, a chain or necklace of conidia 

 being formed at the tip of each branch of the stalk. There are 

 many species of Penicillium. Besides the blue one, there are 

 others which are green, brown, pink, red and white. Some 



* 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 fertil- 

 ization. 



j" Hymenium. 



J Apothecium. 



Perithecium. These fruit bodies of the Ascomycetes are sometime called 

 ascocarps, i.e., sac fruits. 



