ZYGOMYCETES 105 



the complete contents of tlie hypha passing into the 

 sporangium (Fig. 33, C); or it may produce zoospores 

 within itself; these little bodies ultimately escaping, 

 and each one developing into an ordinary Pythium 

 plant. 



Cystofus candidus, the " White Eust," also one of 

 the Oomycetes, lives parasitically on Shepherd's Purse 

 {Caf sella Bursa-pastoris) and other cruciferous plants. 

 The hjrphee grow in the intercellular spaces of the host 

 plant, and send out tiny suckers, which penetrate 

 into the cells and absorb their contents. Asexual 

 spores are formed just beneath the epidermis of Ihe 

 host; they cause chalky- white blisters to appear on 

 flowers, leaves and stem, and much distortion of the 

 parts attacked. The blisters burst and liberate the 

 spores, which in the mass appear as a white powder. 

 Under a proper temperature and in the presence of 

 sufficient moisture, the contents of the spores divide 

 into bicUiated zoospores, from which new plants arise. 

 Sexual reproduction also occurs, the antheridia and 

 oogonia being formed on parts of the mycelium deeply 

 situated in the host. The fertilized ova are resting- 

 spores, and are set free by the decay of the host. 



The group of Fungi known as Zygomycetes 

 (Grr. zygon, a yoke; myJces, a fungus) are so named 

 because the sexual process is somewhat analogous to 

 that of the Conjugatse among the Algae (p. 34) ; branches 

 of the mycelium conjugate — that is, are " yoked " 

 together — and their contents fuse, the result being a 

 Zygospore. The mould which commonly grows upon 

 bread, but also appears upon horse-dung and other 

 bases, is usually Mucor mucedo. A supply for observa- 



14 



