OF SOUTH AUSTRALIA. 
41 
of dividing the large number of species into more or less smaller groups or genera 
whose members showed in common major characteristics suggesting that they 
were closely related phylog'enetieally, i.c., during the course of evolution, to 
each other. It thus came about that a genus Lepiota characterised by white spores, 
a free hvmenophore (the stem being readily “dislocated” from the cap), a ring 
on the stem and no volva was considered as having closer affinities with, as being 
more nearly related to, all the other genera with white spores than with the genus 
PsaUiola, to which the common mushroom belongs, which differs only in having 
purplish-brown instead of white spores. As many species of these two genera 
are so like each other in general appearance, habitat, etc., that it is necessary to 
ascertain the colour of the spores before being able to decide to which one they 
belong, it seems more likely that in the course of evolution the change in colour 
of the spores was a later event than the possession of a volva or ring. Also, if 
the spore-colour changes were the first to appear, then one would have to consider 
the other features .just considered (volva, ring, eta.) as having occurred (or 
perhaps rather as having disappeared) in several different lines of descent, 
spontaneously and almost simultaneously, by a process of convergent evolution, 
a phenomenon that: does occur in nature but does so only rarely, and is very 
unlikely to do so along several different lines of descent. Rea has consequently 
placed close together, as showing intimate relationship, the genera with a free 
hymenophore, then those with a volva and ring, or a volva only, or a ring only 
and so on with the other characteristics, leaving the spore colour as a final means 
of separating what may be called sister genera. The old classification was an 
artificial though convenient one, but that adopted hv Rea shows the relationship 
more truly. An ideal classification is one which will show clearly the true 
relationships between the various families, genera, etc., concerned— passing from 
the less differentiated and presumably more archaic forms to end with the most 
highly specialised — and at the same time be convenient. Though agreeing as 
to the correctness of the classification that Rea adopted in dealing with the 
agarics, we have decided as a matter of convenience to follow the older method 
of dividing the agarics primarily according to llic colours of the spores. 
We have also decided to follow the older classification in leaving the Soldi 
with the Polypori generally as a group characterised by a pore-bearing hymeninm. 
We do this not only as a matter of expediency, but also because we think that 
they are closely related phylogenetically. 
P. Claussen, in Bngler and Prantl’s “Die Naturliehen Pflanzenf amilien , ’ ’ 
(1 Band, 1928, gives the following main classification of the fungi. 
DIVISION EUMYCES (EUNGI). 
Class I. — Rhyoomycetes. (Moulds, &c.) 
Class II. — Ascojiycetes. (Spores developed in small sacs or asei.) 
C la s s I II. — -Photo m y cet f. s . 
Class I V. — BAsinroAtYcETES. 
Sub-class 1. Demibasidii (Smut’s and Rusts). 
Sub-class 2. Eubasidii (Mushrooms, Puff-balls, etc.). 
Iu the present work we are concerned with Sub-class 2, Eubasidii, of Class IV. 
(Basidiomycetes). A few large and striking species of Class II. (Ascomycetes) 
will also be considered as coming under the heading of the larger fungi. 
'Phe Sub-class 2, Eubasidii, comprises a single Order, the Hymen o mycetea e, and 
this is subdivided by Claussen into seven Sub-orders. These seven Sub-orders 
may be placed in the two divisions employed by Rea, the Heterobasidine com- 
prising the Sub-order Trent ollineae, and the Homobasidiae, including the rest' of 
these Sub-orders. The Homobasidiae, following Rea in part, may lie divided 
again into the Gasteromycetaies, comprising his Sub-orders Phalli neat*, Nidularineae, 
Lycoperdiueae, Tiynienogastrineae, and Scleroderma tinea e, in which the hymeninm 
is enclosed with a covering or peridium at maturity, and into the Hymenomycetales, 
comprising his Sub-order ITymenoniyeetmeap, in which the hymeninm is fully 
exposed at maturity though it may be enclosed in the young stage. 
In this Handbook, it has been decided to combine sonic of the features of the 
classifications adopted by Rea and by Claussen. To the former’s “British 
Basidiomyeetae ” we are indebted for most’ of the tabular arrangement and 
definitions above specific rank. 
In the case of genera which are not defined by Rea because they do not occur 
in Britain, S. Killermann, in Mugler and Prantl’s “Die Naturliehen Pflanzen- 
familien, ” 6 Band, 1928, has in the main been followed. The arrangement and 
definitions in the Gasteromycetaies are those adopted by Dr. G. TI. Cunningham. 
