332 FUNGOUS DISEASES OF PLANTS 



twig cankers the gloeosporial stage of the apple bitter rot fungus 

 may produce these. Moreover, in artificial cultures species of Colle- 

 totrichum have also yielded ascigerous stages referable to the genus 

 Glomerella. 1 On the other hand there is a fairly close relationship 

 between extreme forms of Colletotrichum and Volutella. 



In members of both Colletotrichum and Gloeosporium it has long 

 been known that when conidia germinate in a drop of water on a 

 glass slide, or under certain other conditions, structures resembling 

 secondary or resting spores may be formed. Hasselbring 2 has 

 made a special study of these and concludes : 



The spore-like organs formed by the germ tubes of the anthracnoses are 

 adhesion organs, by means of which the fungus is attached to the surface of 

 its host during the early stages of infection. They are not suited for dissemi- 

 nation and therefore are not to be regarded as spores. The adhesion discs are 

 formed as a result of stimuli from mechanical contact acting on the germ tubes. 

 When growing in nutrient media the germ tubes lose their power of reacting 

 to contact stimuli by the formation of appressoria. Under natural conditions 

 the appressoria are formed as soon as the germ tube emerges from the spore. 



XXXIII. ANTHRACNOSE OF GRAPE 

 Gloeosporium ampelophagum Sacc. 



Scribner, F. L. Report on Fungous Diseases of the Grape Vine. Anthrac- 

 nose. Division of Botany, U. S. Department of Agriculture, Built. 11 : 

 34-38. pi. 6. 1886. 



Viala, T. Les Maladies de la Vigne. Anthracnose. pp. 204-247. pis. 5-6. 

 figs. 60-73. 1893. 



The anthracnose or bird's-eye disease of the grape is a striking 

 disease now well distributed throughout Europe and America. It 

 was not observed extensively in the United States until about 1885, 

 and there are few localities in which it has become a malady so 

 constant in succeeding seasons as the black rot or the downy 

 mildew. It is, however, a disease which may cause great injury 

 when it becomes epidemic, particularly in view of the fact that it 

 is not so readily treated. 



The disease occurs upon berries, shoots, and leaves, but is far more 

 common upon shoots and berries. Upon the latter the well-known 



1 Edgerton. Bot. Gaz. 46, /. c. 



2 Hasselbring, H. H. The Appressoria of the Anthracnoses. Bot. Gaz. 42 : 

 135-142. figs. 1-7. 1906. 



