INJURIES INDUCED BY PLANTS 57 



promptly pulling up or otherwise eradicating the diseased plants, 

 and partly in isolating the infected area by means of narrow 

 trenches. As a general and most important measure, it is 

 advisable at once to remove from the wood all plants attacked 

 by fungi, so that their spores may not spread infection. Tidiness 

 is the first hygienic law in sylviculture. 



Having noted above the more important points that should be 

 kept in view in studying the parasitic fungi, I shall now, in 

 accordance with the plan of this work, pass on to a systematic 

 examination of the parasites that occur in woody plants. 

 As regards fungi that are parasitic on farm or garden crops, I 

 shall shortly refer only to such as are of general practical 

 importance. For plant-parasites not included in this work I 

 must refer to the handbooks of Frank or Sorauer. 



Following the most recent classification of the fungi, which 

 distinguishes three groups namely, Phy corny cetes (Algal fungi), 

 Ascomy cetes, and Basidiomy cetes I shall, begin with the first 

 group. This embraces five orders namely, Zygomycetes, 

 Entornophthorece, Saprolegiacece, Peronosporece Chytridiacece, and 

 UstUaginea.* 



Of these orders there are only two that need be considered 

 here. 



PERONOSPOREJE 



The Peronosporea are true vegetable parasites, whose mycelium 

 ramifies in the tissues of higher plants, the hyphse being for the 

 most part intercellular, though occasionally also intracellular. 

 Special absorbing organs (haustoria) are employed for abstracting 

 the nutriment from the living cells, which consequently die after 

 a shorter or longer period. The sporophores which spring from 

 the mycelium either grow through the stomata or burst through 

 the epidermis. These in various ways form sporangia, which 

 produce gonidia, often motile. 



Having moved about for some time in a drop of water as 

 swarm-spores, the gonidia develop a germ-tube, though the 

 sporangia may also germinate directly without having first 

 produced swarm-cells in their interior. 



* [For details as to the classification of fungi the reader may be referre d 

 to the text-books of De Bary, Zopf, and Von Tavel. ED.] 



