TRANSACTIONS OF SECTION K. 581 
Various theories as to origin of gonidia. Culture experiments with lichen 
spores undertaken by Tulasne which seemed to prove that the gonidia were 
directly formed at the tips of the colourless hyphz within the lichen thallus. 
Finally Schwendener’s announcement of the dual theory of the lichen thallus : 
that the gonidia were alge of independent origin outside the thallus, and that 
the lichen was therefore a composite plant formed from a fungus more or less 
parasitic on the gonidia or alge. 
Synthetic cultures undertaken by various workers to test Schwendener’s 
theory with the result that in time numerous lichen plants were successfully 
developed, up to the fruiting stage, from lichen spores associated with alge. 
Discussion thereafter centred on the exact nature of the association between the 
two organisms : whether parasitism of the fungus on the alga or a condition of 
mutual benefit described by Reinke as consortism, by De Bary as symbiosis? 
Various forms of contact between the two symbionts described and the effect on 
the alga. 
The problem really one of nutrition. The fungus is certainly dependent on 
the alga; but the alga is also dependent on the fungus for nitrogen, and to 
some extent for carbohydrates as proved by recent research on the nutrition of 
alga and lichen gonidia in varying conditions. Other instances cited of benefit 
afforded to green plants by associated fungi. 
2. The Contamination of Drinking Water by Alge and its Removal. 
By Professor T. Jounson, D.Sc. 
An account was given of an important supply of water (360 million gallons) 
rendered highly objectionable for domestic use by the presence of a blue-green 
alga, Oscillatoria tenuis var. natans, which was shown, by dredging, to breed in 
the mud of the reservoir floor. Subsequently the weed floats and causes ‘ water- 
bloom ’ or ‘ breaking of the meres.’ Its accumulation in stored water gives it an 
oily, fishy odour, and also puts the filter-beds out of action. 
One to 10 lb. of copper sulphate per 1,000,000 gallons removes the nuisance 
without injuring man or fish, as Moore and Kellermann first showed 
The paper illustrated the necessity of supplementing the usual chemical and 
bacteriological examination of water with a biological one. 
SYDNEY. 
FRIDAY, AUGUST 21. 
After the President had delivered his Address (see p. 560), the following 
Papers were read :— 
1. The Species Concept, with especial reference to Eucalyptus. 
By J. H. Maren. 
The paper opened with a statement that the subject, though often debated in 
Europe and America, has been rarely discussed in Australia. The difficulties 
presented by homoplasy were then referred to. The proposition of no fixed line 
of demarcation between species was then discussed, and the writer’s use of 
concentric circles to illustrate the affinities of allied species was referred to. 
The difficulties presented by such large genera as Hieracium, Aster, Salix, and 
Rubus, as well as Lucalyptus, were then emphasised. 
The aid of anatomy and physiology, and indeed other methods, in our quest 
for truly natural species was then discussed. The Jordanian species were 
referred to, and Darwin’s dictum was quoted that as regards species our troubles 
come from trying to define the indefinable. Species-making being a form of 
empiricism, there are two camps of honest workers, the ‘splitters’ and the 
‘lumpers,’ and the mistakes that are made are the result of existing conditions. 
The writer then explained in detail, as regards Eucalyptus, the plan of his 
