The South Aiistralid(n Naturalist, 
65 
grows and feeds. If the thallus w^ere not chinked in this way tiie 
lihcen would be seriously injured during weather changes, by 
cracking, 
Fruticulous and foliaceous forms of lichens appear to be more 
advanced than crustaceous ones. They grow^ on more fertile 
surfaces, and possibly these better conditions have produced the 
more highly differentiated type of thallus. These species grow 
attached to their substratum by means of small root-like struc- 
tures sent out from their lower surface. This surface in higher 
forms is the absorptive region, because the upper surface, being 
so exposed, is protected by a waxy covering to prevent excessive 
water loss. 
Lichenology is a very wide subject, and at present in Aus- 
tralia is not an easy subject for investigation. There are so-many 
species that the mere use of generic names is misleading. More- 
over a study of lichen forms divorced from their habitat is greatly 
to be deprecated, so that the lichenologist must also be an ecologist 
if valuable work is to be done. 
Lichens which live inside rocks are of special interest. One 
species makes its way into limestone rocks. The great importance 
of these forms is obvious. They initiate the breaking down of 
rocks. The lichen makes its way into the rock, and nothing but 
the small reproductive cups reach the surface of the rock. These 
cup-like hollows left by the apothecia soon enlarge under atmos- 
pheric influences. ^ Moss spores may germinate in them and also 
higher forms of lichen growth. Organic matter accumulates in 
these hollows, preparing the soil for larger plants. From this it 
will be seen that the pioneering work of crustaceous lichens is of 
great importance m the making of a plant habitation from bare 
surfaces. 
AN ARBORETUM FOR ADELAIDE. 
Adelaide, with its genial climate, can grow the trees of the 
growth^'^^ warm temperate regions, as well as many of tropic 
Thanks to the energy of Mr. A. W. Pelzer, the City gardener, 
anf already growing in our streets, parks, 
we a?e kindness of Mr. A. Morison 
Mpm ■ ^ planted along the War 
ITev r‘^ Adelaide Bridge and Frome Bridge, 
hey comprise the following species : 
^nghsh Ash tree {Fraxinus excelsior) 
halse Acacia {Robinia pseud-acacia) 
beoten Elm {Ulmus Montana Dover) 
