276 SUMMARY OF RESULTS [ch. 



crowded in a close hemisphere. These features indicate advance; but the 

 sorus of these species has reached the point of mechanical dead-lock, for the 

 sporangia often lack space to open and shed their spores. None of the 

 known Gleicheniaceae have surmounted this difficulty (Vol. II, p. 204, Figs. 

 486-488). Attention is thus directed to the Cyatheaceae, which also have 

 superficial sori, often unprotected {Alsophild), and with habit, anatomy, and 

 venation not markedly different in the simpler types from the more advanced 

 Gleicheniaceae. They have adopted a gradate sorus and lateral dehiscence, 

 which solves the dead-lock mechanically. The next question will be whether 

 all Cyatheaceae share this. Exceptions are found in Presl's genera Lophosoria 

 and Metaxya, latterly merged in Alsophila; each is represented by a single 

 species. These genera are now re-established as substantive genera, and are 

 included in the new Family, Proto-Cy atheaceae (Chapter XXXIl). They appear 

 to take their places at the base of certain distinct phyletic lines, which have 

 met the mechanical difficulty in different ways: Lophosoria leading to the 

 Cyatheoids, and Metaxya to a less extensive series which may be styled the 

 Metaxyoid Ferns (Chapters xxxili and XLVi). 



Lophosoria is really one of the Simplices, for all the sporangia of its sorus 

 arise simultaneously on a receptacle corresponding in position to that of 

 Gleichenia (Fig. 548). The upright axis is covered with hairs and slightly 

 dictyostelic, but solenostely is prominent in its horizontal runners. It is in 

 fact a compact upright shoot closely related anatomically to D. {Gl.)pectinata, 

 with which also the fertile pinnae agree (Figs. 547-550). The sorus, however, 

 compares rather with that o( D.{Gl.) linearis (Figs. 487, 550): but essential 

 differences lie in the lateral dehiscence of the sporangia, and in the smaller 

 spore-output. The large size of the sporangia, however, and the ill-differen- 

 tiated stomium, suggest that Lophosoria represents an amendment on the 

 sporangia of Gleichenia: they open outwards, and the spores are readily shed. 

 It may be held as one of the advanced Simplices, with near relation to 

 Gleichenia, but with features of Alsophila seen in the upright habit and 

 lateral dehiscence. Hitherto it has been included in Alsophila. Clearly it is 

 a synthetic type, leading to the Cyatheaceae rather than actually one of them. 



The Cyatheoid Ferns, while maintaining the habit of LopJiosoria, and 

 often developing it to large size with advances in vascular structure, introduced 

 two further changes, viz. the broad chaffy scales in place of hairs, and a 

 gradate sorus and smaller sporangia : in some of them there may also be a 

 basal, partially or completely cup-shaped indusium. All of these are physio- 

 logically probable amendments (Chapter XXXIIl). The prototype of the scale, 

 with its often massive base, is seen in D. {Gl.) pectinata (Fig. 475), and in 

 Lophosoria (Fig. 547). The gradate sorus of Alsophila follows naturally on 

 intercalary elongation of the receptacle (Fig. 564) : an argument in favour 

 of the origin of the basal indusium as a new formation, originating from 



