568 TRANSACTIONS OF SECTION K. 
should turn. It is then specially interesting that Mr. Hamshaw Thomas has 
lately described a new Jurassic Fern, Stachypteris Halli, which has marginal 
sori, and is probably referable to a position like that of Zoxsoma and Thyrso- 
pteris, between the Schizeacee and the Dicksoniee. In fact the gaps in the 
evolutionary series of the Marginales are filling up. We may await with con- 
fidence fresh evidence from the Jurassic Period, upon which Professor Seward is 
directing an intensive interest. 
I should be ungrateful indeed if I did not mention your very full representa- 
tion of Blechnoid Ferns : for developmental material of several of these has been 
sent to me by Dr. Cockayne, and others from New Zealand. A wide compara- 
tive study of the genus has led me to somewhat unexpected results in regard to 
the plasticity of the sorus, its phyletic fusions and disruptions. The consequent 
derivative forms are seen in Woodwardia and Doodya on the one hand, and on 
the other in Scolopendrium and Asplenium. 'These Ferns together constitute a 
coherent phylum springing ultimately from a Cyatheoid source. The details 
upon which this conclusion is based I hope to describe in a separate communica- 
tion to the Section. 
And lastly, the Hydropteridee deserve brief mention. Represented in your 
Flora by two species of Azolla, and one each of Marsilea and Pilularia, they 
typify a condition which must theoretically have existed among Ferns in very 
early times, viz., the heterosporous state. But hitherto, notwithstanding the 
existence of our living Hydropteridez, no fossil Fern with microscopic structure 
preserved had been detected from the Primary Rocks, showing this intermediate 
condition between the homosporous type and that of the Pteridosperms. This 
unsatisfactory position has now been resolved by Professor Lignier, who has 
recently described, under the name of Afittagia, a fossil from the Lower West- 
phalian, which bore sori of which the sporangia contained four megaspores, 
while the outer tissues of the sporangia resembled those of ZLagenostoma. 
Pending the discovery of further specimens, these observations may be welcomed 
as filling with all probability a conspicuous gap in the evolutionary sequence of 
known forms. 
From the rapid survey which I have been able to give you of some of the more 
notable Australasian Ferns of relatively archaic type, it is clear that they have a 
very interesting and direct bearing upon the phylesis of Ferns. The basis upon 
which conclusions as to phyletic sequence are arrived at is at root that of the 
Natural System of Classification generally—the recognition not of one character, 
or of two, but of as many as possible, which shall collectively serve as criteria of 
comparison. In the case of the Filicales we may use the characters of :— 
) External form. 
(1i) Constitution, as shown by simple or complex segmentation. 
i) Dermal appendages, hairs or scales, 
) Stelar structure, simple or complex. 
) Leaf-trace, coherent or divided, 
) Soral position. 
(vii) Soral construction. 
ii) Indusial protections. 
) Sporangial structure, and mechanism of dehiscence. 
) Spore-output. 
) Spore-form, and character of wall. 
(xii) Form of prothallus. 
(xiii) Position of the sexual organs, sunken or superficial 
(xiv) Number of spermatocytes, and method of dehiscence. 
(xv) Embryology. 
In respect of all these criteria progressions of character may be traced as 
illustrated by known Ferns, and probably other criteria may emerge as study 
progresses. In each case, upon a footing of general comparison, checked as 
opportunity offers by reference to the stratigraphical sequence of the fossils, it 
may be possible to distinguish with some degree of certainty what is relatively 
primitive from what is relatively advanced. Thus, the protostele is generally 
admitted to be more primitive than the dictyostele, the simple hair than the 
flattened scale, and a high spore-output than a low one. 
Applying the conclusions thus arrived at in respect of the several criteria, it 
