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 Tremellodendropsis pusio
SynonymsClavaria pusio
Tremellodendropsis transpusio
Tremellodendropsis transpusio var. transpusio
Aphelaria pusio
Pseudotremellodendron pusio
BiostatusPresent in region - Indigenous. Non endemic
Article: Reid, D.A. (1957) [1956]. New or interesting records of Australasian basidiomycetes II. Kew Bulletin 1956: 535-540.
Description: Fruitbodies of the type collection are small, slender, clavarioid plants, up to 1 cm. high, which
are once or twice dichotomously branched. The branches are terete except toward the base of
the sporophores and just beneath the dichotomies where they are somewhat flattened.
In other gatherings, robust, fastigiate specimens up to 7 cm. high occur, in which the lower
branching may be polychotomous, and the subsequent dichotomies more numerous than in
the type. It is sometimes difficult to trace the mode of branching owing to fusion of adjacent
limbs. Fresh specimens vary in colour from white to dull pallid to flesh colour or deep buff,
are of tough, fleshy consistency, and have a high water content (Crawford 1954). When dried
these fungi become brown and horny-cartilaginous. Hyphal structure monomitic, consisting of
generative hyphae 2-3-5 µ wide, with thin or very slightly thickened walls.
These hyphae bear clamps at the septa which may be of a more or less loop-like form.
Hymenium thickening, reaching 156 µ on the main branches of some specimens, but not
distinctly layered. Basidia 2 or 4-spored, tremellaceous. Spores hyaline, smooth, elliptical, but
rather variable in both size and shape. Those of the type are 9-5-12 x 4-5-6 µ, but the
complete range for the species is 9-13 (-16) x 4-5-6-5 (-8-5) µ. Spore germination as seen in
the type specimen consists of the production of a short pointed sterigma about 5 µ long, from
which a secondary elliptical spore 8 x 4 µ, is produced.
Distribution: Distribution. This fungus has been reported under the various names listed above from: New
South Wales, Victoria, Queensland, Australia ; New Zealand ; Tasmania ; Philippines ;
Sumatra ; India ; Madagascar ; and Brazil.
Notes: Crawford (loc. cit.) wrote as follows on the genus Tremellodendropsis " Delimitation of the
species of Tremellodendropsis is difficult ; morphologically they are all very similar, both in
the fresh state and even more so when dried. Differences in size, length of stalk, degree of
flattening of branches, and compactness of plant have been observed, but the growth form is
most probably dependent on environmental conditions. In the related genus Aphelaria a
similar wide range of growth forms has been recorded for A. dendroides. Spore size is
usually regarded as a fairly constant character, but if the basidia produce from one to four
spores a wide range in spore size from any one plant might be expected ". These
observations are in complete agreement with those of the author. However, Crawford
divided the genus into two subgenera on the basis of whether the basidia were cruciately
subseptate at the apex, or whether they had a transverse septum cutting off a cruciately
septate apical region before spore formation, and then used spore size and shape to
distinguish the species. The present author has examined the type specimens of Clavaria
pusio, G. flagelliformis and Thelephora archeri, and has found tremellaceous basidia of the
kind figured by Crawford (fig. III, p. 624) for Tremellodendropsis transpusio in each. The
septation is not visible in the very young basidia, and is not easily seen in the old ones
which have shed spores, as they collapse readily in hymenial squashes. Even so in these old
basidia there is nearly always a constriction at the point where the transverse septum would
be expected, and it is.sometimes possible to see traces o£it projecting from the walls at this
point. It is therefore often difficult to find basidia which clearly show complete septation,
unless the fruitbody is in the correct stage of development, or unless suitable portions are
examined. Nevertheless in some specimens of the type collection of C. pusio the basidia
are well preserved and the septation easily seen. The description of T. transpusio by
Crawford was thus quite unjustified, as apart from the structure of the basidium there is
complete agreement in spore size (Crawford gave the spores of T. pusio as 9-16 x 4.5-7 µ
and those of T. transpusio as 9-15 x 4-7 µ).
It has been found that there is exceptionally wide variation in spore size and shape in any
one fruit-body. This is probably due in part to basidia producing from one to four spores as
Crawford suggests, but in very few of the collections examined was there any close
approach to the uniformity of spore size and shape as shown (fig. I, p. 620) for her various
taxa. Indeed the spores of the type specimen of G. flagelliformis exhibited particularly wide
variation in shape, with a high percentage showing the ovoid form of her var. ovalispora,
and she herself states that the spores of this variety vary from subcylindrical to subglobose.
There is considerable variation also in the size and shape of the spores of Thelephora
archeri in which the majority are 9-12 x 4-5-6 µ, but a few are 11 x 7-5-8 µ. Spore
measurements in these fungi are further complicated by spore germination with the
production of smaller secondary spores on the parent plant. This may account for the lower
range of spore size given by Crawford for T. flagelliformis, especially as she shows (fig. I
(c), p. 620) a spore of T. flagelliformis var. tasmanica which has germinated to produce a
typical pointed sterigma. With the exception of the var tasmanica, in which the spores
appear to be somewhat larger, it seems. pointless to retain varieties based on these variable
spore characters.
With regard to the type of Thelephora archeri it should be noted that Corner (1950) stated
that "Lachnocladium archeri (Berk.) Bres. = Thelephora archeri Berk." and Cunningham
(1953) wrote " The type labelled " Tasmania ", was referred by Bresadola to
Lachnocladium; but Corner (1950, p. 723) Correctly showed it to be a Thelephora. A
second collection on the type sheet ex " Delegate Hill, Vic,, E. Reader ". may be the same
but this could not be ascertained since spores were not found ". It is difficult to see why
these collections should have been referred back to genus Thelephora, as the elliptical
spores are quite smooth, and hyaline or very faintly yellowish when mounted in potassium
hydroxide, and the basidia are tremellaceous.
Crawford, discussing the systematic position of the genus Tremellodendropsis, writes as
follows " Some authors would probably place Tremellodendropsis in the Tremellaceae,
regarding the partial or complete septation of the apical region of the basidium as
anomalous for the Clavariaceae; the subgenus Transeptia might even be placed in the
Auriculariaceae because of the transverse septation. However, transverse septation of the
old basidia occurs not only in members of the subgenus Tremellodendropsis but also in
other members of the Clavariaceae-e.g., Clavulina it is therefore not unreasonable to
suppose that the time of septation occurs earlier in the young basidia of the subgenus
Transeptia. The members of the genera Aphelaria and Tremellodendropsis form a sequence
from the nonseptate elongate clavate basidium, through the still e1ongate clavate but
partially septate basidium, to the " Transeptia" basidium where the apical portion is cut off
by a transverse septum to give a cruciately septate region. All these basidia differ from the
typical Tremellaceous basidia in still being clavate not globular. The genus
Tremellodendropsis provides a link between Clavariaceae, Tremellaceae and
Aruiculariceae". In any consideration of the systematic position of these fungi the structure
of the basidium assumes the greatest importance and so it is essential that a clear idea be
formed of how the basidium develops. The clavate probasidium is cut off by a clamped
basal septum, and continues to enlarge. A secondary septum which lacks a clamp
connection is then formed cutting off an apical portion which becomes longitudinally
septate and functions as the basidium proper, and a basal portion which functions as a stalk
cell. Crawford considers that in the " Transeptia' type of structure described above (and
according to the present author the only type found in Pseudotremellodendron) the term
basidium should include both the longitudinally septate apical portion and the stalk cell. In
the view of of the present author, however, the term basidium should be restricted to the
apical segment, but it seems probable that this type of reproductive structure is a primitive
one in the Tremellaceae. Crawfrd attaches great importance to the shape of the basidia in
Tremellodendropsis and states that they " differ from typical Tremellaceous basidia in still
being clavate, not globular". Whilst this is true, it must be remebered that the tremellaceous
fungus Eichleriella spinulosa {Berk. and Curt.) Burt possesses basidia which are far more
strongly clavate than those found in Pseudotremellodendron pusio. McGuire (1941)
described two Sebacina (S. podlachica Bres., S. umbrina Rogers)'which have exactly
comparable basidia to those described above. He writes of S. podlachia " probasidia at first
clavate, with basal septa and clamps 5-15 µ below the swollen tips, tardily cut off by
secondary septa at the bases of ths swollen tips, finally obovate........ etc. He adds "The
great variation in basidium sizes cited by Bourdot and Galzin is probably due to the fact
that the secondary basal septa are often very difficult to see. It may be that they sometimes
fail even to develop,.... ", etc. Martin (1941) has also described similar basidia in
Protohydnum cartilagineum A. Moll. he writes " The basidia are as Moller describes them,
but he fails to emphasise sufficiently their unusual character. THe probasidia are at first
long clavate (fig. 10), 30-35 µ in length. The terminal portion becomes greatly swollen and
more or les globose, and finally is cut off from the basal stalk, the swollen portion only
becoming divided by oblique or longitudinal septa". His figures, like those of McGuire,
show no clamp at the septum between basidium and stalk cell. Again in Sebacina prolifera
Rogers the basidia are rather similar to those of Pseudotremellodendron and Rogers (1936)
writes of this fungus "It differs from all species of Sebacina known to the author in the
broadened subbasidial cell". The only differences from the Pseudodotremellodendron
basidium is that the septum between the basidium and the subbasidial cell is clamped, and
the subsequent basidial proliferation occurs from this clamp connexion. This probably
represents a more advanced type od reproductive structure in which the secondary septum
of Pseudotremellodendron has been replaced by one that is primary and clamped. In al
genera of the Clavariaceae where the basidium becomes transversely septate, this occurs
after spore dischanrge, and is comparable with the fiormation of secondary septa in the
vegetative hyphae, wheeras in these fungi it occurs before spore discharge, and forms part
of the reproductive structure. In addition to the structure of the basidium, and nearly as
important when deciding to which group of fungi Pseudotremellodendron should be
assigned, is the method of spore germination. In no genus of the Clavariaceae does the
spore germinate directly to produce a secondary spore, but this is a common occurence in
the Tremellaceae. In this connexion it should be noted that Crawford figures (fig. I (c)) a
germinating spore of T. flagelliformis var. tasmanica which has produced the characteristic
pointed sterigma which in T. pusio has been shown to bear the secondary spore, and this is
atxon which she maintains has clavate basidia which are only "cruciately subseptate at the
apex". In view of this evidence the author considers that Pseudotremellodendron should
be placed in the Tremellaceae. He cannot take seriously Crawford's suggestion of a
possible relationship with the Auriculariaceae, from which this genus differs very widely.
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