SUMMARY. 97 



Spraying is, however, the most important general method of pre- 

 venting disease caused by Glomerella. The work of Scott (73) and 

 others with the bitter-rot of apples has shown that the proper appli- 

 cation of Bordeaux mixture will largely protect fruit from this disease. 

 Rolfs (66) has shown that the wither tip of citrus fruits, due to Glom- 

 erella, can also be controlled by spraying. There is no reason to 

 doubt that diseases of other plants caused by the same fungus can be 

 largely prevented by. the proper use of Bordeaux mixture. In deter- 

 mining dates for spraying it is important to first discover the natural 

 infection periods and to spray the plants before infection occurs. As 

 has already been indicated, a considerable part of the infection is 

 brought about by the appressoria or chlamydospores. The germ 

 tube from an appressorium having penetrated the epidermis of the 

 host is apparently beyond the reach of injury by a fungicide; and this 

 infection, though it may remain dormant more or less indefinitely 

 under certain conditions, may also develop and cause serious injury 

 under certain other conditions. The time and method of infection 

 apparently varies in many cases, depending upon conditions which 

 favor the production, dissemination, and germination of the spores. 



SUMMARY. 



(1) Most cultivated fruits and many other economic plants are 

 attacked and seriously injured by fungous parasites of the genus 

 Glomerella. 



(2) These fungi pass through three stages in the course of their 

 complete development and produce three kinds of spores — conidia, 

 ascospores, and chlamydospores or appressoria. Until recently the 

 two principal spore forms, conidia and ascospores, have been described 

 and treated as distinct organisms. 



(3) The conidial stage is most frequently observed and described, 

 and is usually referred to one or the other of the form genera Gloeospo- 

 rium and Collet otrichum. About 500 so-called species of conidial 

 forms probably belonging to Glomerella are recorded. 



(4) The genetic connection of the conidial with the ascogenous 

 stage was first definitely proven with cultures in 1898 by Atkinson, 

 working with Glomerella (Gloeosporium) cingulata (Stonem.) S. and 

 v. S. found on privet. Since that date the life-history forms, races, 

 and species of the organism from several other host plants has been 

 recorded by Clinton, Stoneman, Edgerton, Sheldon, Koorders, and 

 the present writers. 



(5) The life histories of forms from 36 different host plants have 

 been determined and recorded here. In 17 cases they were produced 

 in pure cultures and in the other 19 cases they developed on the host 

 either hi a moist chamber or under natural conditions. In 31 cases 

 they were first reported by the writers. 



46023°— Bui. 252—13 7 



