AUSTRALIAN . FERtfS. , 49 



is D. antarctica, a noble tree fern, first noticed on the summit of 

 Mount Tomah, by Allan Cunningham, and found to measure 

 between thirty and forty feet. Since the days of Cunningham it 

 has been found in other parts of Australia, and Mr. Backhouse, 

 in his " Narrative of a Visit to the Australian Colonies," gives a 

 good representation of one in the plate of a " Fern Valley" in 

 Tasmania. An allied species, D. fibrosa, is also indigenous in 

 New Zealand, where the fibrous coat of the trunk is sliced by the 

 natives and used in constructing houses. In proportion to the 

 size of the caudex, the pinnules of the frond seem very small. 

 Dicksonia dubia (Brown's Davallia dubia) is one of our commonest 

 ferns, and abounds on the banks of our creeks. It seems some- 

 what uncertain as to which genus it belongs, but Hooker thinks, 

 " from analogy, and especially its close affinity with D. straminea, 

 it must be regarded as a Dicksonia" "When the plant is fully 

 developed, and the reflection of the lobule is not very evident, 

 there may be a reasonable doubt as to the propriety of removing 

 it from Davallia ; but a close examination of a young frond in 

 which a two-valved iiidusium may sometimes be traced, seems to 

 settle the question. D. davallioides resembles the last in some 

 respects, but the texture of the frond is more membranaceous, 

 and, as far as I have observed, never attains so large a size. I 

 found an abundance of this species near Tomah, and the late 

 Mr. Macgillivray sent ine some beautiful specimens of it from 

 Clarence Eiver. The remaining Dicksonia is one found by C. 

 Moore, Esq., Director of our Botanical Garden, and named by 

 him D. Young ii, as a compliment to His Excellency the Governor. 

 The genus Hymenopliyllum (from liymen, a membrane, wcApliyl- 

 lon, a leaf, in allusion to the tenuity of the foliage), consists of mi- 

 nute species, sometimes found on moist rocks, and sometimes on the 

 caudices of tree ferns. The sori are marginal, and the involucre 

 of one leaf, more or less deeply two-valved; but in some cases 

 there is a great difficulty in distinguishing between this genus 

 and the next to be considered, for u the receptacle is not always 

 included in Hymenophyllum, nor always exserted in Trichomanes. 

 Again, in the latter genus, there is an approach to a two-lipped 

 involucre, and in the former, it can sometimes be scarcely called 

 two-valved." Dr. P. Mueller is of opinion that Australia possesses 

 only two real species of Hymenoplujllum^ which I suppose are 

 O 



