I] PARASITISM 13 



1909 BuLLER, A. H. R. Researches on Fungi. Longmans, Green & Co., London. 



1909 BuLLER, A. H. R. The Destruction of Wood by Fungi. Sci. Prog, xi, p. i. 



1909 Cutting, E. M. On the SexuaUty and Development of the Ascocarp in Ascophanus 



carneus. Ann. Bot. xxiii, p. 399. 

 1912 Dale, E. On the Fungi of the Soil. Ann. Myc. x, p. 452. 



1912 Dodge, B. O. Methods of Culture and the Morphology of the Archicarp in Certain 

 Species of the Ascobolaceae. Bull. Torrey Bot. Club, xxxix, p. 139. 



1913 GODDARD, H. N. Can Fungi living in Agricultural Soil Assimilate free Nitrogen? 

 Bot. Gaz. Ivi, p. 249. 



1913 McBeth, I. G. and Scales, F. M. Destruction of Cellulose by Bacteria and Fungi. 

 U.S. Dept. of Agr. Bureau of Plant Industry. Bull. 266, New York. 



1914 RamlOW, G. Beitrage zur Entwicklungsgeschichte der Ascoboleen. Myc. Centralbl. 

 Vj p. 537- 



191 5 Baden, M. L. Observations on the Germination of the Spores of Coprinus ster- 

 guilinus, Fr. Ann. Bot. xxix, p. 135. 



191 5 Scales, F. M. Some Filamentous Fungi tested for Cellulose destroying Power. 



Bot. Gaz. Ix, p. 149. 

 1920 Hall, A. D. The Soil. John Murray, London, 3rd ed. (Fairy Rings, p. 278). 



Parasitism 



Facultative Parasites. Several fungi which are capable of passing 

 through their whole development as saprophytes are also occasionally found 

 on living plants as facultative parasites or hemi-saprophytes. It was first 

 shown by de Bary that such fungi possess the power of disintegrating and 

 killing the tissues in advance, so that they are not parasitic in any strict 

 sense, but first kill the cells of their host and then live saprophytically upon 

 the dead remains. This is well seen in Botrytis cinerea, the detailed knowledge 

 of which is due to Blackman and Welsford, and to Brown. When the spores 

 of Botrytis cinerea are placed in a drop of nutrient fluid on the leaves of 

 the broad bean ( Vicia faba), they show the first signs of a germ-tube in 

 2-3 hours ; the outer walls of the developing tube soon become modified to 

 form a mucilaginous sheath by means of which the hypha adheres to its 

 substratum. After growing for a while along the surface of the leaf the 

 germ tube turns down and its tip, filled with dense protoplasm, becomes 

 pressed against the cuticle where it may or may not swell somewhat and 

 become spread out to form an enlargement or simple adpressorium; as 

 growth continues the germ-tube is held firmly in place by its mucilaginous 

 coat and the cuticle is ruptured mechanically by the pressure of its tip. The 

 fungus now penetrates directly into an epidermal cell, or grows more or less 

 horizontally in the subcuticular layers; in either case these layers become 

 swollen, and in doing so appear to stretch the cuticle and make its penetration 

 by other germ-tubes easier. As the hyphae make their way through the 

 epidermis the cells of the palisade parenchyma become affected ; their nuclei 

 begin to disintegrate, the chloroplasts swell, and the starch almost disappears. 

 In the bean a dark coloration is one of the characteristic signs of death, and 



