THE SPECIES OF THE GENUS PENICILLIUM. 333 



As already mentioned, it hardly seems advisable to subdivide 

 this morphological genus at present, even in cases where the 

 course of development of the separate species seems to assign 

 them to different places in the system. Thus, the great difference 

 between the ascospores of P. glaucum, JBref. and P. luteum, Zuk. 

 involves their allocation to two different genera, whilst any 

 species exhibiting true perithecia would have to be placed in 

 a third genus, leaving the numerous unallotted species to rank 

 as "fungi imperfect!" in a fourth group. For this, however, 

 it is preferable to wait until the species are better known, retaining 

 in the meantime the genus Penicillium as a group of species 

 classed together by their conidiophores. 



287. The Species of the Genus Penicillium. 



The species most frequently encountered, generally of technical 

 or pathological importance, will be dealt with first, chief among 

 them being Penicillium glaucum (Link ?), Brefeld ; (Pen c. crusta- 

 ceum, Fries?). The P. glaucum, Link, of the literature is 

 evidently a collective name for a series of closely allied green 

 species, a thorough examination of which is highly desirable. 

 The colour of the growths, the branching of the conidiophores 

 and the size and shape of the conidia are very similar in all. 

 If it be desired to preserve this specific name from extinction 

 it is impossible now to say what Linne, Link, Fries and others 

 had before them it would be most appropriately bestowed on 

 the species more closely studied by BREFELD (II.), which produced 

 very small, spherical conidia (2.5 /j, in diameter), and sclerotia, 

 all differing from this form being named afresh. That a large 

 number of these do exist is sufficiently demonstrated by the 

 recent investigations of THOM (II.) In these circumstances it 

 is difficult to assign to any particular form the numerous reports 

 in the literature relative to the occurrence and action of the 

 collective species " P. glaucum." For instance, the " P. glaucum" 

 concerned in the ripening of cheese can apparei tly be subdivided 

 into several distinct species, readily distinguishable macroscopically, 

 in pure cultures, from each other and from " P. glaucum." Two 

 of them, in fact, are described a little later on, under the names 

 P. Roquefort and P. Camembert. Differing from these again are 

 the species furnishing round spores, and appearing as the cause 

 of decay in ripe fruits, but not yet closely examined. The 

 classification of the so-called P. glaucum, Link, species of green 

 mould observed on hops, shed-ripe tobacco, in the leather manu- 

 facturing process, and in vinous fermentation (the cause of mouldy 

 flavour in wines) will have to be po Opened until they have been 

 more closely compared by the customary mycological methods. 

 This group is comparatively easy to differentiate from the species 

 producing elongated spores (P. luteum, P. italicum, P. olivaceum], 



