THE PKODTJCTION OF PERITHECIA IK GLOMEKELLA. 69 



are formed ? Various explanations and suggestions have been made 

 by different writers at different times, but in most cases there has 

 been no sufficient experimental evidence offered to establish fully 

 any of the theories advanced. A brief review of the various attempts 

 which have been made, and the suggestions offered, may be of some 

 interest in this connection. Klebs (53), Smith (83), Brefeld (14), 

 Stoneman (89), Appel and Wollenweber (1), Butler (16), Gliick (37), 

 Ihssen (48), and others have discussed the subject. 



The production of the sexual fructifications of certain algae and 

 aquatic fungi may perhaps depend primarily upon factors of nutri- 

 tion or environment which can be controlled under cultural con- 

 ditions. The work of Klebs (53), especially, seems to justify such a 

 conclusion. Much more work is necessary, however, to thoroughly 

 verify this and especially to eliminate the possibility of some of the 

 results being due to the use of different races or strains. Kauffmann 

 (50) in the account of his studies on Saprolegnia, expressed the 

 belief that their behavior depended entirely upon definite chemical 

 and physical conditions readily controlled. He also thinks that 

 culture media and conditions could be standardized and safely used 

 as a basis for species segregation. This apparently needs further 

 verification, as Lechmere (57) was unable to obtain the same results 

 with these organisms. 



In the case of the sexual forms of algse some writers have attempted 

 to show that there is a more or less regular periodicity in the appear- 

 ance of the fertile fructifications of different species. Recent inves- 

 tigations by Danforth (22) appear to throw doubt upon the general 

 application of this view also. However the case may be with the algae, 

 there is little or no evidence at present available to show that 

 periodicity is an important factor in the production of the perithecial 

 forms of Glomerella and other pyrenomycetes. In the writers' 

 culture work with Glomerella and other genera, such as Guignardia, 

 Melanops, and Cryptosporella, when mature spores are used, they have 

 been unable to find any relation between the time of the collection or 

 the age of the material and the production of the perithecial forms. 

 Under natural conditions it is known that perithecia are in general 

 most abundantly produced in temperate regions during late winter 

 and spring. 



Brefeld (14) suggested as the result of observations of ascogenous 

 fructifications under natural conditions that their production 

 depended to some extent on the season of the year and the sub- 

 stratum; but in our experience, cultures made from fresh material 

 collected under natural conditions do not produce perithecia any 

 more frequently from material collected at one time than at another. 

 Various experiments in growing different strains of Glomerella and 

 other pyrenomycetes on various substrata do not indicate that this 



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