LOWER DEVONIAN PLANT REMAINS 125 
DISCUSSION 
The various types of plants known from early Palaeozoic rocks 
of Victoria have been described and figured in three papers. Those 
from a number of exposures in the Monograptus beds (Lower 
Ludlow) include Baragwanathia and Yarravia (Lang and Cook- 
son 1935). The chief types from the Centennial beds of the 
Walhalla series are Sporogonites and Zosterophyllum. When 
these were first described (Lang and Cookson 1930) their age 
was believed to be Upper Silurian or possibly Lower Devonian 
(Skeats 1928), but now it is definitely regarded as Lower Dev- 
onian (Thomas 1937, Gill 1942). The collection of plants from 
Mount Pleasant, Alexandra (Cookson 1935) is not as yet definitely 
dated by animal remains. The interest is that it combines in one 
flora types known from the Lower Ludlow horizon (Yarravia) 
with others known from the Lower Devonian horizon of the 
Centennial beds (Zosterophyllum and Pachytheca). 
The flora from Lilydale described in the present paper also 
combines plants from the lower horizon (Yarravia) with others 
from the upper horizon (Sporogonites, Zosterophyllum) but has 
the advantage of being stratigraphically dated. It is this rather 
than the descriptive details of the plant remains themselves that 
constitutes the importance of the Lilydale flora as at present 
known, for in the case of each type better preserved examples are 
known from other localities. 
The small Lilydale flora taken along with the Mount Pleasant 
assemblage provides evidence of the essential similarity of the 
vegetation of Victoria from the Lower Ludlow to the Lower 
Devonian. The composition of this Siluro-Devonian flora in 
Australia of definite land plants with a vascular system and a 
considerable morphological complexity is a fully established piece 
of knowledge concerning early plants. The grade of organization 
of the plants from the Monograptus beds onwards is at least as 
high as that first met with in the Lower Devonian of the Northern 
Hemisphere. It is interesting that there are detailed points of 
agreement in the occurrence of the same generic types (Zostero- 
phyllum, Sporogonites, Pachytheca) or of closely agreeing types 
(Baragwanathia in the Australian flora representing Drepano- 
phycus). 
In the Northern Hemisphere the representation of early vas- 
cular land plants is best and clearest in the upper beds of the 
Lower Devonian or Lower Old Red Sandstone where Psilophyton, 
Drepanophycus, and Zosterophyllum are met with, together with 
other vascular plants and with more anomalous types such as 
Prototaxites, Nematothallus, and Pachytheca. At lower horizons 
