From the first Berkeley was deeply interested in the fungi, and practically all his subsequent work was devoted to this group of plants, and although well versed in general Cryptogamic Botany, it was in the field of Mycology that his laurels were won. A review of the work done can be most conveniently discussed under three separate headings—Systematic Mycology, Morphology and Literature, and Plant Pathology, respectively.
Systematic Mycology.
Under the title British Fungi, four fascicles of dried and well-prepared specimens, numbering in all 350 species, were issued between 1836 and 1843. In those days exsiccatæ were not issued from a commercial standpoint, as is too frequently the case at the present day, but represented the outcome of careful investigation on the part of the author, hence Berkeley's exsiccatæ are at a premium at the present day.
In 1828 Berkeley first corresponded with Sir W. J. Hooker on matters dealing with cryptogams, and in one of his early letters stated that he had devoted much time to the study of fungi, more especially to the extensive genus Agaricus, which at that period included all the gill-bearing fungi. At this time, Sir William was engaged in preparing the volumes dealing with cryptogams, as supplementary to The English Flora of Sir James Edward Smith, and approached Berkeley on the subject of undertaking the section dealing with Agarics, in the volume devoted to the fungi. Berkeley agreed to this arrangement, and was finally induced to describe the whole of the fungi. A footnote at the commencement of the volume by Sir W. J. Hooker is as follows:
"When the printing of the species of this, the 2nd Part of the Class Cryptogamia, was commenced, I thought myself highly fortunate to have obtained the assistance of my valued friend, the Rev. M. J. Berkeley, in preparing the first Tribe, Pileati. I have now to express my cordial acknowledgements (in which I am satisfied I shall be joined by every Botanist in the country) to that gentleman for having kindly undertaken to prepare the whole of this vast family for the press: and it is certain that the task could not have fallen into better hands."
The volume contains detailed descriptions of all British fungi known at the time, amounting to 1360 species, included in 155 genera, the great majority of which had been studied by the author in a living condition, and also compared with specimens contained in various exsiccatæ and with the very extensive collection owned by Sir W. J. Hooker. The appearance of this book at once placed Berkeley in the front rank of Mycologists, and it was universally admitted as the most complete Mycologic Flora of any country extant; and furthermore, so far as accurate information, and a true sense of the conception of species are concerned, the same statement holds good at the present day. At this date our knowledge of extra-European fungi was almost nil, with the exception of a few woody cosmopolitan species collected by various travellers, more as matters of curiosity than for the advancement of our knowledge of the fungus-flora of the world.
Opportunity alone was required by Berkeley, and such opportunity was readily afforded by Sir W. J. Hooker, who placed unreservedly in Berkeley's hands the various collections of exotic fungi received at Kew from time to time. This practice was continued by the two succeeding Directors at Kew, Sir Joseph Dalton Hooker and Sir William Thiselton-Dyer. Such unrivalled opportunities were utilised to the fullest extent by Berkeley, who soon manifested by his treatment of the material placed in his hands a thorough grasp of the subject, and for nearly half a century practically all collections of exotic fungi passed through Berkeley's hands. During this period 6000 new species were described, and in numerous instances illustrated, including many new genera from all parts of the world, arctic, antarctic, tropical and temperate. Botanists were now enabled, for the first time, to grasp the true significance of the fungus-flora of the world, which numerically ranks next to Phanerogams, and which was shown to exercise an influence on life on the globe in general, not realised before Berkeley's time. The better known European genera of fungi, many of which appeared to be sharply defined, and by some mycologists considered to be of ordinal importance, could now be estimated at their true value and relegated to their true position in the scheme of classification rendered possible by a good knowledge of the range of structure presented by the fungi of the world at large. As regards geographical distribution, Berkeley repeatedly emphasized the fact that the fungi are more cosmopolitan than any other known group of plants, and that their abundance at any place during a given period was almost entirely dependent on conditions favouring the development of the higher forms of plant life, fungi only following in the wake of such, and never posing as pioneers, on account of the nature of their food. Amongst the numerous novel types of extra-European fungi described by Berkeley, it is somewhat difficult to indicate briefly even a few of the most striking forms. Perhaps his genus Broomeia stands out pre-eminent. It belongs to the puffball group of fungi, and is unique in that family—the Gasteromycetaceae—in having numerous individuals springing from, and imbedded in a common sterile base or stroma. It is a native of the Cape of Good Hope. The following is Berkeley's dedication of this genus to his friend and co-worker, C. E. Broome, M.A., of Bath. "Nomen dedi in honorem amicissimi, C. E. Broome, armigeri, Tuberacearum Anglicarum accuratissimi indagatoris, cujus pene solius laboribus extant hodie viginti species indigenae fungorum hypogaeorum." Broomeia congregata Berk., is described and figured in Hooker's London Journal of Botany, 1844. Certain club-shaped fungi parasitic on caterpillars, belonging to the genus Cordyceps, occurring on buried caterpillars in New Zealand, are the giants of their tribe, measuring up to eighteen inches in length. Finally, Berkeley first introduced to our notice many of those quaint fungi belonging to the group including our well known "stinkhorn"—Phallus impudicus L.—and cleared up many points in their structure previously unknown. Fries, the most distinguished mycologist of his time, writes as follows in his Preface to Hymenomycetes Europaei; "Desideratissima vero Synopsis Hymenomycetum extra-europearum, qualem solus praestere valebit Rev. Berkeley."
Notwithstanding Berkeley's researches on exotic fungi, a task in itself too comprehensive for most men to grapple with, he continued to study the British fungi, and, mostly in collaboration with his friend, Mr C. E. Broome, published a long series of articles in the Annals and Magazine of Natural History, from 1837 down to the year 1883. In these articles 2027 species of fungi are enumerated, mostly new, or species new to Britain, and consist mainly of critical notes on the morphology and affinities of the fungi under consideration, and will compel the attention of mycologists for all time.
From the above brief account it may perhaps be concluded that Berkeley was essentially a systematist and founder of new species. Owing to the vast amount of material that passed through his hands, he was so perforce, but his leaning was always rather towards the biological and morphological side of the subject.