Leonard — Genus Taenitis, tvith Notes on remaining Taenitidinae. 271 



for the crowding of the leaf-gaps in Blechnum, and the consequent compli- 

 cations of the dictyostele. 



Hand in hand with the simple stele of Taenitis goes also the simple leaf- 

 trace. 



In the leaf, besides the general form, the great point of resemblance to 

 Blechnum is the intra-marginal commissure. It is formed in exactly the 

 same way as that of Blechnum, and, like it, breaks up with the dissolution of 

 the sorus (1). 



A commissure is also seen in the other three genera, but it is not always 

 intra-marginal, an exception being seen in Paltonium. The presence of this 

 commissure is a leading point of resemblance between them and Taenitis. 

 Whether this is a sufficient ground for basing a relationship must not be 

 granted offhand, since a commissure is also found in the Pterid series. It is 

 a point which must be left over until further developmental work, especially 

 on Paltonium, is available. On all other points of comparison the three genera, 

 Drymoglossum, Paltonium, and Hymenolepis, are sufficiently different from 

 Taenitis for us to keep them in a measure apart from it. 



The absence of an indusium in Taenitis is a point of difference from the 

 typical Blechnum ; but in Brainea, which is a Blechnum derivative, the 

 indusium is also absent. It seems probable that in both abortion of the 

 indusium has occurred. 



Taenitis may be regarded as an advanced type, though its scales are 

 relatively narrow, and the stelar structure does not progress beyond a 

 relatively juvenile stage. The well-formed reticulate venation is to be held 

 as an advanced feature. As regards the sorus, it is possible that it has 

 developed from indusiate forms such as Blechnum, but that the sorus 

 protection has been lost in the course of evolution, as is seen to be the case 

 in Brainea. 



A suggestion has been made by Eva Schumann (11) that there is a 

 possible relationship between Taenitis and Pteris. This seems highly 

 improbable, for in Pteris the commissure is marginal, while in Taenitis the 

 commissure is intra-distal with a well-developed venation between it and the 

 margin of the leaf. The fact seems to be that in the Pterids and Blechnoids 

 a similar lateral fusion of sori, into linear fusion-sori, has taken place. But 

 the former are Ferns with their sori marginal ; the latter have their sori 

 superficial. 



Frau Schumann also suggests that the structure of Platytaenia bears the 

 same relation to that of Taenitis as does Acrostichum aureum to Pteris. 

 Platytaenia is certainly a form with an acrostichoid sorus, and comparison 

 indicates Taenitis as a probable point of origin. But it is to be borne in 



SCIENT. PROC. R.D.S., VOL. XV., NO. XXIV. 2 X 



