9 6 GENERAL BIOLOGY 



from organic compounds. A few of them make galls upon 

 green plants (fig. 28). Many more (known as rusts, 

 blights, mildews, etc.) are destructive pests of green 

 plants. But most of them are saprophytes, and assist 

 in the circulation of food materials in the earth by hasten- 

 ing the decomposition of the bodies of dead plants. 



The fruiting stages of the higher fungi are aggregates 

 or integrates of filaments, that rise collectively from 

 mycelia, and fashion together parts of various forms: 

 spheres in the puffballs, with the spores borne inside: 

 low cup-shaped receptacles in some of the disc fungi, 

 or Ascomycetes (fig. 57), with the spores contained in 

 cylindric spore sacs (asci) in a fruiting layer (hymenium) 

 in the bottom of the cup : umbrella shaped caps in mush- 

 rooms, with the spores borne on the vertical surfaces of ra- 

 diating lamellae underneath the cap. 



Study 12. Observations on cultures of yeast and molds. 



Materials needed: A good yeast culture i 'n Pasteur's 

 solution. Several plate cultures of molds of differ- 

 ent ages on gelatine (directions for making plate cultures 

 will be found in any good laboratory, manual of mycol- 

 ogy or of bacteriology). Young mycelia of Mucor, 

 in which streaming of protoplasm may be observed, 



One to three day old cul- 

 tures of Penicillium, in which 

 the germination of the spores 

 may be observed. Old Peni- 

 cillium cultures, in which the 

 spore clusters may be studied. 

 FIG. 57. A disc fungus (Peziza?). /, Study in yeast, i) the 



the aerial part of the fungus, with a pvirlpnrpQ nf 



quarter section cut out to show h, evidences or 



the hymeneum. k, a bit of the fatirm stirl of 

 hymeneum showing, a, ascus, con- T"^ 10 



taining spores; n, sterile paraphyses, n f r>arhrm rliryvi/^o in +Ti/* 

 and m. sub-hymenial tissue. /, a ( CarDOn QlOXiae Ml the 



culture jar. 2) The details 



