Fig. 47. Aspergillus amstelodami: 

 small conidial head and two small 

 perithecia. X375. From Charles 

 Thorn and Kenneth B. Raper, U. S. 

 Dept. Agr. Misc. Pub. 426 (1941). 



100 THE FUNGI IMPERFECTI AND THE ASCOMYCETES 



asci and ascospores readily. In some cases the asci may be few in 

 number and in some species one may find bodies having the general 

 appearance of perithecia but containing no asci. These are known 



as sclerotia and are usually looked 

 upon as being incomplete peri- 

 thecia. 



To identify species of Asper- 

 gillus has been considered an all 

 but impossible task but, as indi- 

 cated in the first edition of this 

 book, the difficulty of identifica- 

 tion is not insurmountable! It 

 would be a simple task for the 

 author to construct some sort of 

 key from Thom and Raper's de- 

 scriptions or to reproduce theirs 

 but, beyond giving the names of 

 the species, little would be gained. 

 Rather the worker is referred di- 

 rectly to their manual.^*' There 

 he will find that by means of a 

 key based primarily upon the color of the conidial heads, the peri- 

 thecia, or the colonies on Czapek's agar, he can readily place his 

 isolate in one of fifteen "species groups." Or he can arrive at the 

 same group by means of another key, based primarily upon morphol- 

 ogy. Then the worker will have to refer 

 to a section devoted to that species group 

 where he will find the fullest kind of de- 

 scription of each separate species. In 

 some cases it is apparent that the identi- 

 fication of species wall be readily made 

 from the keys to species groups and then 

 the diagnosis can be verified from the de- 

 scription itself. In other cases it appears 

 that this will be much more difficult. In 

 all cases the extent of expected variation 

 within a species is indicated, something 

 sadly lacking in many taxonomic treatises. 

 Throughout he will find excellent photo- 

 graphs in abundance, of colonies (many in color) and of morpho- 

 logical details. He will also find exact directions to duplicate the 

 conditions under which the moHs so described and photographed 



Fig. 48. Section through 

 a perithecium of Asper- 

 gillus sp. showing develop- 

 ment of asci and asco- 

 spores. 



