APPENDIX VII 



709 



hence, it is probably widely distributed. Its stolon-producing character is very 

 characteristic and diagnostic. 



PenicilUum italicum (Fig. 247) and P. olhaceum occur on tropic fruits, including 

 pineapples, lemons, oranges, etc. The fungus causes extensive putrefaction in such 

 fleshy fruits as the pineapple. 



PenicilUum brevicaidc (Fig. 248) grows on decayed paper and it has been recom- 

 mended by Gosio for the detection of arsenic, since when grown in media with traces 

 of arsenic, it forms the pungent compound diethylarsine. None of the species of 

 PenicilUum are pathogenic. About six to seven species of this genus are connected 

 with the ripening of cheeses. For example, a little-known Norwegian cheese 

 "Gammelost" has associated with its ripening, according to Johann Olsen, a green 

 mould, PenicilUum aromaticum, and so showing the unsatisfactory state of our 



Fig. 248. — PenicilUum brevicaule. a, Conidiophores and simple chains of conidi- 

 ospores; b, f, more complex conidial fructifications; c, two young chains of conidio- 

 spores; d, e, echinulate conidiospores; g, h, j, sketches of forms and habits of conidial 

 fructifications; k, germinated conidiospores. (After Thoyn.) 



knowledge about these fungi, this fungus may prove on close investigation to be 

 identical with the one which works in Roquefort cheese. 



As all of the species of PenicilUum are readily cultivated and kept for some time in 

 a satisfactory condition for study, they are especially useful in the systematic exercises 

 which are essential in the training of competent mycologists. As the time which can 

 be devoted to such a study is limited, the work can be varied by assigning, as un- 

 knowns, cultures of the different species of the genus Aspergillus to certain members 

 of the class and cultures of PenicilUum as "unknowns" to other members, and it may 

 be advisable to interchange the material, so that all of the students in the class in 

 mycology become acquainted with the similarities, as well as the differences dis- 

 played by fungi of the genera Aspergillus and PenicilUum. It is better to distribute 

 these moulds to the class in culture media in Petri dishes than in test-tubes, because 



