CULTIVATION AND PRESERVATION OF PENICILLIA 69 



the developing colonies are especially favorable for observing the earliest 

 stages of perithecium formation (see fig. 144). Emmons (1935), Dodge 

 (1933), Shear (1934), and Swift (1932), based their studies largel}^ upon 

 this substratum. In our present discussion, notes from corn meal agar 

 cultures commonly form an important part of the diagnosis of ascosporic 

 species. 



Hay Infusion Agar 



Hay infusion agar is very useful for isolating Penicillia from nature 

 since it permits a great number of forms to make a limited growth without 

 particularly favoring the development of any single species. Perithecia 

 usually develop upon this medium, as on corn meal agar, if a strain ex- 

 hibits any capacity whatever to develop an ascosporic stage. In certain 

 species, such as Penicillium javanicum v. Beyma, the medium seems to 

 favor more than most the development of conidial structures as well. 

 Descriptive notes from hay agar cultures are incorporated into the species 

 diagnosis of a few species in this Manual. 



The medium is prepared as follows: 



Distilled water 1000 cc. 



Decomposing hay 50 grams 



Autoclave for 30 minutes at 15 pounds. 



Filter. 



Infusion filtrate 1000 cc. 



K2HPO4 ■. 2 grams 



Agar 15 grams 



Adjust pH to 6.2 ± before final sterilization. 



Wickerham's Antibiotic Test Medium 



Penicillin production is characteristic of the Penicillium chrysogenum 

 series. The production of citrinin is characteristic of P. citrinum. The 

 production of claviformin is characteristic of several species of the Fasci- 

 culata, including P. clavijorme, P. urticae, P. expansum, and others. While 

 the production of these antibiotics cannot be taken as sole or conclusive 

 proof of relationships, proof that one of them is produced often affords 

 a strong indication of such ties. A simple, bacterial-spectrum test for 

 (1) revealing the production of antibiotics and (2) differentiating between 

 penicillin, citrinin, and claviformin has been successfully devised by our 

 associate. Dr. L. J. Wickerham. This test consists of a simple determina- 

 tion of the relative inhibition of selected test organisms by growing mold 

 cultures (see p. 75). It has repeatedly proved valuable in our present 

 taxonomic studies, particularly in the assignment of strains showing the 

 general morphology of P. citrinu^n. The culture medium upon which the 

 mold cultures, and subsequently the bacterial test strains, are grown, has 



