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The first large group of fungi chosen for investigation by the methods described in Part II was the Aspergillus group. The Aspergilli were chosen primarily because they are relatively easy to grow on synthetic media and because a wide variety of cultures was available in different parts of the world. Throughout this work conditions have been kept as nearly standard as possible so that results obtained at any time during the progress of the work should be comparable. With this end in view all the metabolism experiments were carried out at one temperature, namely, 23-25° C. One medium, consisting of a Czapek-Dox medium of the composition given in Part I, p. 7, was used throughout. This medium was made up in large amounts and pipetted out accurately, in 250 c.c. quantities, into a number of 750 c.c. conical flasks.

Decaying oranges or other citrus fruits are almost invariably infected by one of two moulds, viz., P. digitatum Saccardo (= P. olivaceum Wehmer), which causes the olive-coloured rot, and P. italicum Wehmer, which is responsible for the blue-green rot. It has been found in the course of work that each of these species has very definite biochemical characteristics which are described in this paper.

In 1907 Saito isolated from the finely powdered mycelium of Aspergillus oryzœ , grown on steamed rice, an organic acid which he was unable to identify, but which, from a general consideration of its chemical properties, he supposed to be β-resorcyl carbonic acid. Yabuta (1912), from the results of analysis, ascribed to the acid the empirical formula C 12 H 14 O 8, and gave to it the name “ kojic acid.” He described its preparation from the mycelium of Aspergillus oryzœ , grown on rice, and also from “ Koji,” and pointed out that it gives an intense wine red colour with ferric chloride solution, which may be recognized even at a dilution of 1 : 200,000. Of interest from a mycological point of view is Yabuta’s observation that kojic acid is produced by a few other species of Aspergillus , but not by the majority, nor by species of Penicillium or Mucor .

The work described in Part III of this series, dealing with the preparation of carbon balance sheets for species of Aspergilus , was continued on exactly the same lines, using species of Penicillium as the organisms for study. The methods used were exactly the same as those described in Parts II and III, the same medium being used, the same temperature of incubation, 23°-25° C. and the same methods of cultivation and analysis. The results obtained are given in the following pages and are arranged in groups according to the classification of the Penicillia adopted by Thom in his recent book ‘ The Penicillia ’ (The Williams and Wilkins Co., 1929). The whole of the cultures of Penicillium, amounting in all to about a hundred species, were sent to Dr. Thom and were examined by him. In some cases these cultures are described in his book and in all cases Dr. Thom gave his opinion as to the correct names to be applied to the different species. The history of the species used and Dr. Thom’s comments on them will be found in an Appendix at the end of this paper. We desire to take this opportunity of thanking Dr. Thom for his very kind co-operation.

Mannitol (C 6 H 14 O 6 ) is the most common of the naturally occurring hexahydric alcohols. It is a curious fact that while glucose is the most commonly occurring hexose, the corresponding alcohol, sorbitol, is of relatively uncommon occurrence, while mannose and fructose, which are structurally related to mannitol, are not of such common occurrence as glucose. Mannitol is a common constituent of many plants, but occurs principally in the curious plant exudation known as “ manna,” and is at present produced technically by two methods, both of which are open to obvious disadvantages. (a) From “manna” (b) By the bacterial fermentation of fructose.

In view of the encouraging results obtained from the preparation of carbon balance sheets for a number of species of Aspergilus , as reported in Part III, the work was extended to other groups and, by way of contrast, carbon balance sheets were prepared for a considerable number of species of Fusarium . It is evident from Wollenweber’s “ Monograph on the Fusaria '*(see ‘ Phytopathology ’ (1913), Vol. 3, p. 24) that the classification of the Fusaria on morphological grounds is very difficult. It was hoped that, as a result of the preparation of carbon balance sheets, some biochemical classification on the lines of the Aspergillus group might be possible, and in order to ensure that the cultures used were authentic, almost the whole of those chosen for investigation were Wollenweber’s own cultures purchased from the Centraalbureau voor Schimmelcultures at Baarn. The methods of investigation adopted were those described in Part II and applied to the Aspergillus group in Part III. The following is the history of the species of Fusarium used in this work :— *(1) F. viride (Lechm.) Wr., Catalogue No. Ag. 81. Purchased from Centraalbureau voor Schimmelcultures at Baarn. *(2) F. solani Mart. var. minus Wr., Catalogue No. Ag. 83. Purchased from Baarn. (3) F. lini Bolley, Catalogue No. Ag. 60. Purchased from British National Collection of Type Cultures, No. 1082. *(4) F. Martii App. et Wr., Catalogue No. Ag. 77. Purchased from Baarn. (5) F. species , Catalogue No. Ag. 80. Isolated at Ardeer from infected potato haulm. (6) F. dianthi Prill, et Del., Catalogue No. Ag. 69. Purchased from British National Collection of Type Cultures No. 1136. *(7) F. uncinatum Wr., Catalogue No. Ag. 75. Purchased from Baarn. ’•‘(8) F. trichothecioides Wr., Catalogue No. Ag. 73. Purchased from Baarn. *(9) F. tubercularioides (Corda) Sacc., Catalogue No. Ag. 72. Purchased from Baarn. *(10) F. coerulm (Lib.) Sacc., Catalogue No. Ag. 65. Purchased from Baarn. *(11) F. salicis Fuck., Catalogue No. Ag. 69. Purchased from Baarn. *(12) F.javanicum Koorders, Catalogue No. Ag. 78. Purchased from Baarn. *(13) F.falcatum App. et Wr., Catalogue No. Ag. 82. Purchased from Baarn. *(14) F. avenaceum (Fr.) Sacc., Catalogue No. Ag. 76. Purchased from Baarn. (15) F. sporotrichoides Sherb., Catalogue No. Ag. 58. Purchased from British National Collection of Type Cultures, No. 1296. *(16) F. sambucinum Fuck., Catalogue No. Ag. 70. Purchased from Baarn. (17) F. vasinfectum Atk., Catalogue No. Ag. 71. Purchased from Baarn. *(18) F. rhizophilum Corda, Catalogue No. Ag. 74. Purchased from Baarn. *(19) F. metachroum Ap p . et W r ., Catalogue No. Ag. 68. Purchased from Baarn. (20) F. species , Catalogue No. Ag. 61. Isolated at Ardeer from a rotting potato. *(21) F. orthoceras App . et W r ., Catalogue No. Ag. 66. Purchased from Baarn. (22) F. scirpi P amr et Fautr., Catalogue No. Ag. 79. Purchased from Baarn. (23) F. oxysporum Schlecht, Catalogue No. Ag. 67. Purchased from Baarn. Fifteen of the cultures in the above list which are marked with an asterisk were Wollenweber’s cultures purchased from Baarn. The carbon balance sheets prepared for these species are given in Tables I and II.