MYXOMYCETES OF THE SAN FRANCISCO REGION

THE MYXOMYCETES have received scant attention in California. Plunkett (1934) published a list of species found in the southern part of the state (within a 150-mile radius of Los Angeles) but to the authors' knowledge no systematic or extensive collections have been made in the northern section of the state. It seemed of interest, therefore, to ascertain the species that are to be found in the vicinity of San Francisco. Since the floras of northern and southern California are in general quite dissimilar, somewhat different spectra of myxomycetous flora might be anticipated for the two sections of the state, although one might expect less difference in the case of slime molds than in other classes of plants since, due to their habit of growth and their habitat, the myxomycetes are not subject to such great variations in environmental circumstances as are flora of higher groups. The present list is not intended as final or complete. It merely represents the species and varieties that have been found since December, 1942, on a number of excursions to likely hunting grounds during appropriate seasons'of the year. Most of the species that are listed have been found in Sutro Forest adjoining the University of California Medical Center in San Francisco. All of the species have been collected within twenty-five miles of San Francisc'o. The nomenclature and order of classification are according to the system of MacBride and Martin (1934). The list contains sixty-eight different species or varieties, representing eleven families and twenty-one genera. Of these species, thirty-one were listed by Plunkett (loc. cit.) from southern California. Many of the remaining thirty-eight species appear to be new to California although previously described from Washington, Oregon, or British Columbia. Nine of the species appear to be new to the Pacific coast. Although final conclusions cannot be drawn from the limited observations that are available, it is interesting to note that thirty-eight of the species or 53.6 per cent of those listed in the present tabulation were not observed by Plunkett (loc. cit.) during six years of collecting in southern California while fiftysix species or 64.4 per cent of those listed by him have not been observed as yet in the San Francisco region. Absence of a species from one list or the other certainly does not prove that the species does not occur in the respective region of the state, but it may be taken as reasonable evidence that the species is not'common or abundant there. The limited data that are available seem to indicate that more intensive and thorough searching for these interesting organisms may well demonstrate myxomycetous populations of quite different composition in the northern and southern parts of California. 1 Received for publication July 12, 1944. It has been suggested that for many species of myxomycetes the texture and moisture content of the substratum on which the sporangia form are more constant and of greater physiological significance than is the species of the substratum,,(Pratt, 1934). Therefore, in the present list an attempt has been made roughly to characterize the substratum on which the specimens were found. For convenience each of the different species has been placed in one of three groups as follows: