SEXUAL AND ASEXUAL REPRODUCTION 



245 



Examples of spore formation in molds have already been 

 described (page 97), two methods having been mentioned. 

 In Mucor (Fig. 42 E) the spores are pro- 

 duced within a sac called a sporangium, 

 while in Penidllium (Fig. 42 A) they are 

 only the ends of branches, growing in the 

 air. The latter are called conidia to dis- 

 tinguish them from spores formed in spo- 

 rangia. The nature and function of spores 

 and conidia are the same. 



Another well-known illustration of the 

 same is the common puffball. This is a 

 colorless plant, growing from a mycelium 

 which lies chiefly below the surface of 

 the ground. At certain seasons of the 

 year there arise from the mycelium, 

 rounded knobs which 

 rapidly increase in size. 

 They may grow as 

 large as a walnut or 

 an orange, and in some 

 species they reach a 

 diameter of a foot, or 

 even two feet ; see Fig. 

 115. Within this great 

 mass the contents di- 

 vide into millions of spores, and after they 

 have been properly matured an opening 

 appears at the top and the spores emerge in 

 the form of a fine dust. The slightest touch 

 upon the puffball will throw masses of dust 

 into the air, from which arises the name puff- 

 ball. This dust consists of millions of minute spores, each of 

 which can become a new plant. 



This power of producing spores is widely distributed among 



FlG. 114. TWO SEG- 

 MENTED WORMS, 

 WHICH MULTIPLY BY 

 ASEXUAL METHODS 



A, Autolytus, multiplying 

 by division; B, Syllis, multi- 

 plying by budding, the buds 

 growing from the side and 

 breaking away to form new 

 individuals. 



FlG. 115. A PUFF- 

 BALL SHOWING 

 THE SPORES PRO- 

 TRUDING FROM 

 THE OPENING 



