The genus PeniciUium has been separated by Raper & Thom (1949) in their Manual of the Penicillia into four major sections, Monoverticillata, Asymmetrica, Biverticillata-Symmetrica and Polyverticillata. The section Asymmetrica is further divided into five subsections: Divaricata, Velutina, Lanata, Funiculosa and Fasciculata. The subsection Asymnietrica-Fasciculata, in its turn, is subdivided into ten series, one of which, the P. cycloqpium series, contains four accepted species and one variety, i.e. P. cyclkpium Westling, P. cyclopium West. var. echinuk&tum Raper & Thom, P. puberulum Bainier, P. martensii Biourge, and P. aurantio-viren.s Biourge. The P. cyclopium series has proved to be of considerable biochemical interest. In 1913, Alsberg & Black isolated from laboratory cultures of P. puberulum a metabolic product which they. named penicillic acid. Birkinshaw, Oxford & Raistrick (1936) isolated from Westling's type strain of P. cyclopium considerably larger yields of penicillic acid and established its molecular structure (structure I). Birkinshaw & Raistrick (1932), working with Alsberg & Black's strain of P. puberulum, showed that, after almost 20 years in laboratory culture, this strain now gave much smaller yields of penicillic acid than were reported by Alsberg & Black. In addition, however, two new metabolic products, puberulic and puberulonic acids, were isolated. The same two acids were also isolated by Birkinshaw & Raistrick (1932) from P. aurantio-virena and by Oxford, Raistrick & Smith (1942b) from P. johannioli Zaleski (=P. mnwrtensii Biourge). Penicillicacid,-puberulicacidandpuberulonic acid have significant antibacterial activity, particularly against Gram-positive bacteria (Oxford, Raistrick & Smith, 1942 a, b). Birkinshaw & Raistrick (1932) and Barger & Dorrer (1934) prepared a number of derivatives and breakdown products of puberulic and puberulonic acids but were unable to advance plausible structural formulae for them. Dewar (1945), in a novel attempt to interpret this experimental evidence and additional evidence on stipitatic acid (Birkinshaw, Chambers & Raistrick, 1942), suggested that 611 VoI. 50 612 J. H. BIRKINSHAW, H. RAISTRICK, D. J. ROSS AND C. E. STICKINGS I952 and mono-2:4-dinitrophenylhydrazone; one COOH group indicated by conductometric titration, which accounts for the liberation by cyclopolic acid of carbon dioxide from aqueous sodium bicarbonate and which is esterified in methyl cyclopolate monomethyl ether; one CH2OH group, vicinal to the COOH group, to account for the formation of cyclopolide with the loss of one molecule of water. On this hypothesis the formula for cyclopolic acid may be written C*. (OCHI). (CH,). (OH). (CHO). (COOH). (CH20H) = CIH120*. Cyclopolic acid

PenicilliUm stipitatum Thom was described as a new species by Emmons [1935]. It grows well on the ordinary solid culture media giving yellow, orange or even reddish orange colonies. The most marked morphological characteristic of the fungus is its very free production of yellow ascocarps.We have found that when this species is grown on the well-known Czapek-Dox solution the metabolism solution gives a characteristic deep red colour with ferric chloride. The metabolic product which is responsible for this colour has been isolated in considerable yield and, since it has not been described previously, we propose to name it stipitatic acid.

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