Bower.—Studies in the Phytogeny of the Fi tic ales. VII. 67 
indusia! flaps, as in Lindsay a. It shows a gradate sequence of sporangia, 
passing soon to a mixed condition. 
9. Paesia viscosa , like P. scaberula , has a typical solenostele. Its 
marginal sorus is usually two-lipped, but shows inconstancy of the inner 
(abaxial) indusium. 
10. Lonchitis shows in vascular characters, in investiture, in venation, 
and in soral features an intermediate position between the bi-indusiate types 
and the genus Pteris. » 
11. Pteris (Histiopteris) incisa closely resembles Pteridium in habit; 
it is advanced as regards scales and venation, but it is less complex in 
stelar condition. Its fusion-sorus shows fluctuations from the exact marginal 
origin, while the inner indusium is absent. After signs of basipetal sequence 
of sporangia the sorus passes over to the mixed condition. 
12. The genus Pteris (excluding Doryopteris ) has superficial scales 
as well as hairs. Its stelar structure is either solenostelic or some near 
derivative, sometimes with a high degree of elaboration (P. podophylld). 
The leaf-trace may be a single or double strap. The venation is frequently 
reticulate. The fusion-sorus is superficial in origin, and the inner (abaxial) 
indusium is absent. The succession of sporangia is mixed. All these 
characters indicate advance upon the Lind say a-Paesia type. 
13. No support is found for Mettenius’s theory of the origin of the 
inner indusium by fusion (connatus) of hairs. On the other hand, it 
appears that isolated hairs may in some cases replace a decadent inner 
indusium. 
14. Acrostickum praestantissimum and A. aureuin appear to be 
* Acrostichoid ’ derivatives of Pteris , sprung from some Litobrochia-ty^e, 
such as P. (L.) splendens. 
15. It has thus been shown that either the outer (adaxial) or the inner 
(abaxial) indusium may be abortive in the Pterid series. In the Dicksonioi- 
deae steps of abortion of the inner indusium are seen in Dennstaedtia , 
Hypolepis , Polypodium punctatmn , and Monachosorum subdigitatum. 
16. In Hypolepis and Monachosorum the outer (adaxial) indusium may 
receive a vascular supply from the receptacle, and appear flattened as 
a marginal lobe of the pinnule. 
17. Phyletically Hypolepis and Monachosorum are derivatives of the 
Dicksonioid-Dennstaedtioid series. Acrophorus and Cystopteris are dis¬ 
tinguished from these by their scales and advanced dictyostely, and are 
related to the Nephrodioid Ferns. 
18. The large series of the Dicksonioids are characterized, by the sori 
maintaining their identity as discrete developments on the separate endings 
of the veins. They have dermal hairs, not scales, excepting their Davallioid 
derivatives. 
19. The Dicksonioids probably sprang ultimately from some Schizaeoid 
