THE FUNGI 



549 



[Chap. XLIV 



twenty egg cells, and by the development of antheridia containing sperm 

 nuclei. The union of a sperm nucleus and an egg nucleus results in a 

 zygote. Upon germination the zygote divides internally and forms motile 

 spores. From these motile spores new hyphae may develop under favor- 

 able conditions. Hyphae may develop, however, from unfertilized eggs — 

 another example of parthenogenesis in plants. It has recently been dis- 

 covered that four hormones are necessary to sexual reproduction in one 

 of the water molds (Figs. 238 and 239). 



Fig. 240. A, blue mold {Penicillium) ; B, green mold {Aspergillus). The spores 

 (conidia) are formed by successive abstrictions of the tips of upright hyphae. 



Blue and green molds. This group of molds was named on the basis 

 of the color of the spores of some of the more common species. Certain 

 of the blue molds are important because of the flavor and color they give 

 to some of our highly esteemed varieties of cheese, such as Camembert 

 and Roquefort. Besides cheese, they can digest and subsist upon a large 

 number of other substances. These fungi and others are the causes of 

 the decay of vegetables, fruits, and meats, both in storage and during 

 transportation, and they occasion enormous monetary losses. They are 

 aerobic and may grow on the surface of moist jelly, and on the surface 

 of wine in a bottle when the stopper is imperfect. 



The hyphae of these fungi have cross walls. The mycelium is a felt- 

 like meshwork on the substrate. Upright hyphae develop, and from 

 their brush-like branching tips numerous one-celled spores are formed 



