The North American Species of Pholiota

Intergeneric Relationships

In our opinion the genus Pholiota originated from Galerina or Galerina-like species. We find in Galerina the development of an apical pore in the basidiospores, and all degrees of development from a thin spot termed a callus to a pore which in a few species is broad enough to cause the apex to be obscurely truncate—in other words a pore about the size found in most species of Pholiota. In Galerina we also find the subhymenium gelatinizing in a few smooth spored species. The same may be said for gelatinous layers in the pileus cuticle but we do not consider this as important in intergeneric relationships as the others because most genera of Agarics show some degree of cuticle gelatinization. To us the important feature between the two genera is the shift in emphasis of the important characters.

GALERINA

PHOLIOTA

1) Spore apex, a fair number with pore more or less distinct.

1) Pore characteristic of most species.

2) Subhymenium. Gelatinous in a few species.

2) Gelatinous in most species.

3) Pileus cuticle gelatinous in some part, less than 25% of species.

3) Over 75% of the species.

4) Spore color yellow to fulvous in great majority.

4) Dark brown to cinnamon brown in great majority, yellow to tawny in a few.


In other words, the features which appear in Galerina have become combined to be characteristic of the genus in Pholiota. This spells out a probable direction of evolution that is difficult to deny and does not bring into the discussion any gastromycetous ancestors. Just as Pholiota has evolved in several directions so has Galerina and it is in one of these lines that we find the trend toward Pholiota. Pholiota mutans, P. discolor and P. striatula approach Galerina so closely that when monographing the latter genus the question arose as where to place them. A second major trend in Galerina is toward or into Cortinarius. G. odorata and G. cortinarioides are readily mistaken for small Cortinarii. If this connection is accepted, it is of course logical to place Pholiota beside Galerina in the Cortinariaceae.

If we now consider the species placed in Hemipholiota and Phaeonaematoloma we can find direct trends toward the Strophariaceae; since the yellow pigmentation, the apical germ-pore of the spore and particularly cystidial types are all found in the Strophariaceae in about the same pattern. If one disregards the color of the spore deposit, he has no features left by which Pholiota can be distinguished from the Strophariaceae. We are concerned here with many species so it cannot be claimed that there are only a few intermediates. As features relating Pholiota to "Geophila" we find that most of the rusty brown spored species with a truncate spore-apex have small spores which exhibit a slight tendency to become compressed (P. vernalis). In Psilocybe, to which this stirps connects many more species have compressed spores so here again we have a situation in which certain characters prominent in one genus are found in a less developed state in a related, presumably more primitive, genus.

As to chrysocystidia, we find them in many more different states of development from species to species in Pholiota than in "Geophila" where they are more uniform as to the nature of the inclusion. Here however the claim cannot be made that this cystidial type is more "primitive" in Pholiota and more advanced in "Geophila" because in the number of species involved and in the diversity of this type of cystidium both are large groups and show about the same gamut of changes. In other words in a comparison of subg. Phaeonaematoloma and "Geophila" as to chrysocystidia and related types, the two groups merge rather evenly. This might be used as an argument for dividing Pholiota and placing those species with chrysocystidia and related types in "Geophila," but it must be remembered that the type of Pholiota has these cystidia as well as lacking gelatinous layers in the pileus cuticle. Consequently we have adhered to the classical distinction between the two—the color of the spore deposit—as being the most useful feature and the one leaving us with the fewest intermediate species.

Pachylepyrium Singer (1957) is to our minds a superfluous genus. It is admitted that when Singer erected it it seemed quite distinct but in view of the present study, like Kuehneromyces, it falls by the wayside. There are a number of species in Pholiota with thick walled (0.5 µ±) spores dark in color—P. pulchella as already mentioned, so this feature appears in viscid as well as dry species. In fact it is found occasionally throughout the genus. The character follows about the same pattern of appearance as thickened cystidial walls, only species with the latter are concentrated in one section by definition.

The subject of relationships should not be dropped, however, without a few comments concerning Inocybe. Like certain other genera, this one is an anomaly in that it is readily recognized at sight by the "Inocybe aspect" and yet when its important macroscopic and microscopic features are put down on paper the recognition of the genus from the description is most difficult. If we eliminate the species with angular to nodulose spores as not presenting a problem, we find the basic features of the smooth spored species to read very much like those of Pholiota in a number of respects. The color of the spore deposit is not too different (clay-color to yellow-brown or earth-brown); cheilocystidia are practically universally present, pleurocystidia are frequently present, and veil development is copious in a number of species.

The points of difference are that to our knowledge gelatinizing hyphae in the subhymenium are not found in Inocybe and few if any species have a viscid pileus caused by the hyphal walls of the epicuticular hyphae gelatinizing. Actually, Inocybe is conspicuous among the large brown-spored genera because of the lack or almost complete lack of the last mentioned feature. Also, the over-all picture from an ecological standpoint is different. Inocybe like Cortinarius is a conspicuously terrestrial genus. Pholiota is a conspicuously lignicolous one—so much so that one retains reservations in his own mind even in regard to species which are described as terrestrial. The pileus surface is also quite different—in most Inocybe species it is of dry matted radial fibrils quite different from the non-viscid Pholiota species. In Inocybe lamprocystidia are common, in Pholiota they are limited to a single section and may be regarded as not so clearly differentiated. We do not know of any Inocybe species with true chrysocystidia. Our over-all impression of the two genera, then, is that any similarities between them are more likely explained as parallelisms than as indicating close relationship. This conclusion is in line with that of previous authors and has not been supplanted by the additions to Pholiota included in the present treatise.

Lastly, a few comments on the gastroid genus Nivatogastrium are in order. When Singer and Smith (1959) described this genus they related it to Pholiota and nothing we have discovered since has indicated a different alignment. The gelatinous layer in the glebal trama was described as hymenopodium, whereas the subhymenium was described as cellular and non-gelatinous. The homologies as we see them now are that the gelatinous layer we have termed subhymenium corresponds to the hymenopodium in Nivatogastrium. This is not a contradiction, in fact it is very likely a situation brought about by the gastroid condition. It is common in the Hymenogastraceae for the one to three cells below a basidium to inflate greatly thus producing a layer, whereas in Pholiota cells in a similar position do not enlarge to form a layer and in fact are continuous with the gelatinous layer. By definition the subhymenium is the layer giving rise to the hymenium.

The real problem, however, is: How does Nivatogastrium fit into the picture of evolution to or from Pholiota? We believe the genus is a gastroid extension of Flammuloides. It is difficult to visualize a lignicolous fungus fruiting under the cold conditions of the snow-line in the mountains having its direct ancestors hypogeous in the soil. More important, however, is the fact all major anatomical characters connect to Flammuloides and we know of no hypogeous species with such a combination of features. Hence we regard the genus as a reduced agaric.